What is lazy initialization and why is it useful?
What is lazy initialization of objects? How do you do that and what are the advantages?
.net
add a comment |
What is lazy initialization of objects? How do you do that and what are the advantages?
.net
add a comment |
What is lazy initialization of objects? How do you do that and what are the advantages?
.net
What is lazy initialization of objects? How do you do that and what are the advantages?
.net
.net
edited Mar 16 '12 at 22:45
user166390
asked Jun 11 '09 at 0:23
SNASNA
3,204103857
3,204103857
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9 Answers
9
active
oldest
votes
Lazy Initialization is a performance optimization where you defer (potentially expensive) object creation until just before you actually need it.
One good example is to not create a database connection up front, but only just before you need to get data from the database.
The key reason for doing this is that (often) you can avoid creating the object completely if you never need it.
33
It should go without saying, but just in case he missed it: The reason it's an optimization is because you often find you don't need to do the creation at all, and because you might save doing some work when the computer is already busy until a time when it is less busy.
– Joel Coehoorn
Jun 11 '09 at 0:42
Good comment. I've amended the answer to incorporate your point.
– Bevan
Jun 11 '09 at 7:53
a very good (and different) use-case/reason for usingLazy
is posted in the following SO question : stackoverflow.com/a/15894928/4404962 this suggestion solved exactly what we needed to solve - usingLazy
as the key principal
– lev haikin
Mar 20 '18 at 13:29
add a comment |
As others have mentioned, lazy initialization is delaying initialization until a component or object is used. You can view lazy initialization as a runtime application of the YAGNI principle - "You ain't gonna need it
"
The advantages from an application perspective of lazy initialization are that users don't have to pay the initialization time for features they will not use. Suppose you were to initialize every component of your application up front. This could create a potentially long start time - users would have to wait dozens of seconds or minutes before your application is ready to use. They're waiting on and paying for initialization of features they may never use or not use right away.
Instead, if you defer initializing those components until use time, your application will start up much quicker. The user will still have to pay the startup cost when using other components, but that cost will be amortized across the run of the program and not condensed into the beginning, and the user may associate the initialization time of these objects with the features they are using.
Too bad I could give only +1! Good rationale, BTW.
– Rajendra Uppal
Jul 17 '11 at 4:50
1
YAGNI means "you ain't gonna need it[the feature, the code]". Lazy initialization is an optimization that is a feature in itself. I would rather say that it applies the other way around: unless you know for sure you need lazy initialization, don't use is, YAGNI.
– Flavius
Oct 29 '18 at 14:45
add a comment |
Lazy Initialization is the concept of deferring object creation until the object is actually first used. If used properly, it can result in significant performance gains.
Personally, I've used Lazy Initialization when creating my own hand-rolled ORM in .NET 2.0. When loading my collections from the database, the actual items in the collection were lazy initialized. This meant that the collections were created quickly, but each object was loaded only when I required it.
If you're familiar with the Singleton pattern, you've probably seen lazy initialization in action as well.
public class SomeClassSingleton
{
private static SomeClass _instance = null;
private SomeClassSingleton()
{
}
public static SomeClass GetInstance()
{
if(_instance == null)
_instance = new SomeClassSingleton();
return _instance;
}
}
In this case, the instance of SomeClass is not initialized until it is first needed by the SomeClassSingleton consumer.
Remove the explicit private variable setting to 'null' to improve the speed slightly further ;). Anyway, it's redundant.
– nicodemus13
Mar 24 '11 at 15:27
nice point, SomeClassSingleton must be equal or lower class of SomeClass
– Fredrick Gauss
Jan 19 '13 at 9:39
what about thread safety for this singleton class?
– Rasika Perera
Aug 22 '14 at 18:23
I don't know if anyone reads old responses but i assume the private static get instance method should be public?
– Biscuit128
Aug 27 '14 at 8:03
@Biscuit128 - I do read them, and yes it should be. I updated it just in case anybody else still reads this.
– Justin Niessner
Aug 27 '14 at 14:25
|
show 1 more comment
In general computing terms, 'lazy evaluation' means to defer the processing on something until you actually need it. The main idea being that you can sometimes avoid costly operations if you turn out to not need it, or if the value would change before you use it.
A simple example of this is System.Exception.StackTrace. This is a string property on an exception, but it isn't actually built until you access it. Internally it does something like:
String StackTrace{
get{
if(_stackTrace==null){
_stackTrace = buildStackTrace();
}
return _stackTrace;
}
}
This saves you the overhead of actually calling buildStackTrace until someone wants to see what it is.
Properties are one way to simply provide this type of behavior.
1
This is not thread-safe.
– Cristi Diaconescu
Aug 11 '10 at 12:48
2
True, but I am not sure why you would be sharing a reference to an exception among multiple threads anyway.
– Dolphin
Aug 11 '10 at 15:36
add a comment |
Here you can read about Lazy Initialization with sample code.
When you have an object that is
expensive to create, and the program
might not use it. For example, assume
that you have in memory a Customer
object that has an Orders property
that contains a large array of Order
objects that, to be initialized,
requires a database connection. If the
user never asks to display the Orders
or use the data in a computation, then
there is no reason to use system
memory or computing cycles to create
it. By using Lazy to declare
the Orders object for lazy
initialization, you can avoid wasting
system resources when the object is
not used.
When you have an object that is
expensive to create, and you want to
defer its creation until after other
expensive operations have been
completed. For example, assume that
your program loads several object
instances when it starts, but only
some of them are required immediately.
You can improve the startup
performance of the program by
deferring initialization of the
objects that are not required until
the required objects have been
created.
add a comment |
Lazy initialization of an object means that its creation is deferred until it is first used. (For this topic, the terms lazy initialization and lazy instantiation are synonymous.) Lazy initialization is primarily used to improve performance, avoid wasteful computation, and reduce program memory requirements. These are the most common scenarios:
When you have an object that is expensive to create, and the program might not use it. For example, assume that you have in memory a Customer object that has an Orders property that contains a large array of Order objects that, to be initialized, requires a database connection. If the user never asks to display the Orders or use the data in a computation, then there is no reason to use system memory or computing cycles to create it. By using Lazy to declare the Orders object for lazy initialization, you can avoid wasting system resources when the object is not used.
When you have an object that is expensive to create, and you want to defer its creation until after other expensive operations have been completed. For example, assume that your program loads several object instances when it starts, but only some of them are required immediately. You can improve the startup performance of the program by deferring initialization of the objects that are not required until the required objects have been created.
Although you can write your own code to perform lazy initialization, we recommend that you use Lazy instead. Lazy and its related types also support thread-safety and provide a consistent exception propagation policy.
add a comment |
//Lazy instantiation delays certain tasks.
//It typically improves the startup time of a C# application.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LazyLoad
{
class Program
{
static void Main(string args)
{
Lazy<MyClass> MyLazyClass = new Lazy<MyClass>(); // create lazy class
Console.WriteLine("IsValueCreated = {0}",MyLazyClass.IsValueCreated); // print value to check if initialization is over
MyClass sample = MyLazyClass.Value; // real value Creation Time
Console.WriteLine("Length = {0}", sample.Length); // print array length
Console.WriteLine("IsValueCreated = {0}", MyLazyClass.IsValueCreated); // print value to check if initialization is over
Console.ReadLine();
}
}
class MyClass
{
int array;
public MyClass()
{
array = new int[10];
}
public int Length
{
get
{
return this.array.Length;
}
}
}
}
// out put
// IsValueCreated = False
// Length = 10
// IsValueCreated = True
add a comment |
As what I have understood about lazy init so far, is that the program does not load/request all data a once. It waits for the use of it before requesting it from eg. a SQL-server.
If you have a database with a large table joined with a large amount of subtables and you dont require the details joined from the other tabels unless going into "edit" or "view details", then Lazy Init. will help the application to go faster and first "lazy load" the detailsdata upon needed.
In SQL or LINQ you can set this "setting" on your database model pr. dataelement.
Hope this makes any sense to your question?
A webclient (eg. a browser) does the same thing. The images are "lazy loaded" after the HTML and AJAX is also a "sort of lazy init" if used right.
add a comment |
The database examples that have been mentioned so far are good, but it's not restricted to just the data access layer. You could apply the same principles to any situation where performance or memory can be a concern. A good example (although not .NET) is in Cocoa, where you can wait until the user requests a window to actually load it (and its associated objects) from the nib. This can help keep memory usage down and speed up the initial application load, especially when you're talking about things like Preferences windows that won't be needed until some later time, if ever.
add a comment |
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9 Answers
9
active
oldest
votes
9 Answers
9
active
oldest
votes
active
oldest
votes
active
oldest
votes
Lazy Initialization is a performance optimization where you defer (potentially expensive) object creation until just before you actually need it.
One good example is to not create a database connection up front, but only just before you need to get data from the database.
The key reason for doing this is that (often) you can avoid creating the object completely if you never need it.
33
It should go without saying, but just in case he missed it: The reason it's an optimization is because you often find you don't need to do the creation at all, and because you might save doing some work when the computer is already busy until a time when it is less busy.
– Joel Coehoorn
Jun 11 '09 at 0:42
Good comment. I've amended the answer to incorporate your point.
– Bevan
Jun 11 '09 at 7:53
a very good (and different) use-case/reason for usingLazy
is posted in the following SO question : stackoverflow.com/a/15894928/4404962 this suggestion solved exactly what we needed to solve - usingLazy
as the key principal
– lev haikin
Mar 20 '18 at 13:29
add a comment |
Lazy Initialization is a performance optimization where you defer (potentially expensive) object creation until just before you actually need it.
One good example is to not create a database connection up front, but only just before you need to get data from the database.
The key reason for doing this is that (often) you can avoid creating the object completely if you never need it.
33
It should go without saying, but just in case he missed it: The reason it's an optimization is because you often find you don't need to do the creation at all, and because you might save doing some work when the computer is already busy until a time when it is less busy.
– Joel Coehoorn
Jun 11 '09 at 0:42
Good comment. I've amended the answer to incorporate your point.
– Bevan
Jun 11 '09 at 7:53
a very good (and different) use-case/reason for usingLazy
is posted in the following SO question : stackoverflow.com/a/15894928/4404962 this suggestion solved exactly what we needed to solve - usingLazy
as the key principal
– lev haikin
Mar 20 '18 at 13:29
add a comment |
Lazy Initialization is a performance optimization where you defer (potentially expensive) object creation until just before you actually need it.
One good example is to not create a database connection up front, but only just before you need to get data from the database.
The key reason for doing this is that (often) you can avoid creating the object completely if you never need it.
Lazy Initialization is a performance optimization where you defer (potentially expensive) object creation until just before you actually need it.
One good example is to not create a database connection up front, but only just before you need to get data from the database.
The key reason for doing this is that (often) you can avoid creating the object completely if you never need it.
edited Jun 11 '09 at 7:52
answered Jun 11 '09 at 0:25
BevanBevan
31k870123
31k870123
33
It should go without saying, but just in case he missed it: The reason it's an optimization is because you often find you don't need to do the creation at all, and because you might save doing some work when the computer is already busy until a time when it is less busy.
– Joel Coehoorn
Jun 11 '09 at 0:42
Good comment. I've amended the answer to incorporate your point.
– Bevan
Jun 11 '09 at 7:53
a very good (and different) use-case/reason for usingLazy
is posted in the following SO question : stackoverflow.com/a/15894928/4404962 this suggestion solved exactly what we needed to solve - usingLazy
as the key principal
– lev haikin
Mar 20 '18 at 13:29
add a comment |
33
It should go without saying, but just in case he missed it: The reason it's an optimization is because you often find you don't need to do the creation at all, and because you might save doing some work when the computer is already busy until a time when it is less busy.
– Joel Coehoorn
Jun 11 '09 at 0:42
Good comment. I've amended the answer to incorporate your point.
– Bevan
Jun 11 '09 at 7:53
a very good (and different) use-case/reason for usingLazy
is posted in the following SO question : stackoverflow.com/a/15894928/4404962 this suggestion solved exactly what we needed to solve - usingLazy
as the key principal
– lev haikin
Mar 20 '18 at 13:29
33
33
It should go without saying, but just in case he missed it: The reason it's an optimization is because you often find you don't need to do the creation at all, and because you might save doing some work when the computer is already busy until a time when it is less busy.
– Joel Coehoorn
Jun 11 '09 at 0:42
It should go without saying, but just in case he missed it: The reason it's an optimization is because you often find you don't need to do the creation at all, and because you might save doing some work when the computer is already busy until a time when it is less busy.
– Joel Coehoorn
Jun 11 '09 at 0:42
Good comment. I've amended the answer to incorporate your point.
– Bevan
Jun 11 '09 at 7:53
Good comment. I've amended the answer to incorporate your point.
– Bevan
Jun 11 '09 at 7:53
a very good (and different) use-case/reason for using
Lazy
is posted in the following SO question : stackoverflow.com/a/15894928/4404962 this suggestion solved exactly what we needed to solve - using Lazy
as the key principal– lev haikin
Mar 20 '18 at 13:29
a very good (and different) use-case/reason for using
Lazy
is posted in the following SO question : stackoverflow.com/a/15894928/4404962 this suggestion solved exactly what we needed to solve - using Lazy
as the key principal– lev haikin
Mar 20 '18 at 13:29
add a comment |
As others have mentioned, lazy initialization is delaying initialization until a component or object is used. You can view lazy initialization as a runtime application of the YAGNI principle - "You ain't gonna need it
"
The advantages from an application perspective of lazy initialization are that users don't have to pay the initialization time for features they will not use. Suppose you were to initialize every component of your application up front. This could create a potentially long start time - users would have to wait dozens of seconds or minutes before your application is ready to use. They're waiting on and paying for initialization of features they may never use or not use right away.
Instead, if you defer initializing those components until use time, your application will start up much quicker. The user will still have to pay the startup cost when using other components, but that cost will be amortized across the run of the program and not condensed into the beginning, and the user may associate the initialization time of these objects with the features they are using.
Too bad I could give only +1! Good rationale, BTW.
– Rajendra Uppal
Jul 17 '11 at 4:50
1
YAGNI means "you ain't gonna need it[the feature, the code]". Lazy initialization is an optimization that is a feature in itself. I would rather say that it applies the other way around: unless you know for sure you need lazy initialization, don't use is, YAGNI.
– Flavius
Oct 29 '18 at 14:45
add a comment |
As others have mentioned, lazy initialization is delaying initialization until a component or object is used. You can view lazy initialization as a runtime application of the YAGNI principle - "You ain't gonna need it
"
The advantages from an application perspective of lazy initialization are that users don't have to pay the initialization time for features they will not use. Suppose you were to initialize every component of your application up front. This could create a potentially long start time - users would have to wait dozens of seconds or minutes before your application is ready to use. They're waiting on and paying for initialization of features they may never use or not use right away.
Instead, if you defer initializing those components until use time, your application will start up much quicker. The user will still have to pay the startup cost when using other components, but that cost will be amortized across the run of the program and not condensed into the beginning, and the user may associate the initialization time of these objects with the features they are using.
Too bad I could give only +1! Good rationale, BTW.
– Rajendra Uppal
Jul 17 '11 at 4:50
1
YAGNI means "you ain't gonna need it[the feature, the code]". Lazy initialization is an optimization that is a feature in itself. I would rather say that it applies the other way around: unless you know for sure you need lazy initialization, don't use is, YAGNI.
– Flavius
Oct 29 '18 at 14:45
add a comment |
As others have mentioned, lazy initialization is delaying initialization until a component or object is used. You can view lazy initialization as a runtime application of the YAGNI principle - "You ain't gonna need it
"
The advantages from an application perspective of lazy initialization are that users don't have to pay the initialization time for features they will not use. Suppose you were to initialize every component of your application up front. This could create a potentially long start time - users would have to wait dozens of seconds or minutes before your application is ready to use. They're waiting on and paying for initialization of features they may never use or not use right away.
Instead, if you defer initializing those components until use time, your application will start up much quicker. The user will still have to pay the startup cost when using other components, but that cost will be amortized across the run of the program and not condensed into the beginning, and the user may associate the initialization time of these objects with the features they are using.
As others have mentioned, lazy initialization is delaying initialization until a component or object is used. You can view lazy initialization as a runtime application of the YAGNI principle - "You ain't gonna need it
"
The advantages from an application perspective of lazy initialization are that users don't have to pay the initialization time for features they will not use. Suppose you were to initialize every component of your application up front. This could create a potentially long start time - users would have to wait dozens of seconds or minutes before your application is ready to use. They're waiting on and paying for initialization of features they may never use or not use right away.
Instead, if you defer initializing those components until use time, your application will start up much quicker. The user will still have to pay the startup cost when using other components, but that cost will be amortized across the run of the program and not condensed into the beginning, and the user may associate the initialization time of these objects with the features they are using.
edited Feb 26 '18 at 0:33
RBT
8,933671100
8,933671100
answered Jun 11 '09 at 0:46
MichaelMichael
46.9k595128
46.9k595128
Too bad I could give only +1! Good rationale, BTW.
– Rajendra Uppal
Jul 17 '11 at 4:50
1
YAGNI means "you ain't gonna need it[the feature, the code]". Lazy initialization is an optimization that is a feature in itself. I would rather say that it applies the other way around: unless you know for sure you need lazy initialization, don't use is, YAGNI.
– Flavius
Oct 29 '18 at 14:45
add a comment |
Too bad I could give only +1! Good rationale, BTW.
– Rajendra Uppal
Jul 17 '11 at 4:50
1
YAGNI means "you ain't gonna need it[the feature, the code]". Lazy initialization is an optimization that is a feature in itself. I would rather say that it applies the other way around: unless you know for sure you need lazy initialization, don't use is, YAGNI.
– Flavius
Oct 29 '18 at 14:45
Too bad I could give only +1! Good rationale, BTW.
– Rajendra Uppal
Jul 17 '11 at 4:50
Too bad I could give only +1! Good rationale, BTW.
– Rajendra Uppal
Jul 17 '11 at 4:50
1
1
YAGNI means "you ain't gonna need it[the feature, the code]". Lazy initialization is an optimization that is a feature in itself. I would rather say that it applies the other way around: unless you know for sure you need lazy initialization, don't use is, YAGNI.
– Flavius
Oct 29 '18 at 14:45
YAGNI means "you ain't gonna need it[the feature, the code]". Lazy initialization is an optimization that is a feature in itself. I would rather say that it applies the other way around: unless you know for sure you need lazy initialization, don't use is, YAGNI.
– Flavius
Oct 29 '18 at 14:45
add a comment |
Lazy Initialization is the concept of deferring object creation until the object is actually first used. If used properly, it can result in significant performance gains.
Personally, I've used Lazy Initialization when creating my own hand-rolled ORM in .NET 2.0. When loading my collections from the database, the actual items in the collection were lazy initialized. This meant that the collections were created quickly, but each object was loaded only when I required it.
If you're familiar with the Singleton pattern, you've probably seen lazy initialization in action as well.
public class SomeClassSingleton
{
private static SomeClass _instance = null;
private SomeClassSingleton()
{
}
public static SomeClass GetInstance()
{
if(_instance == null)
_instance = new SomeClassSingleton();
return _instance;
}
}
In this case, the instance of SomeClass is not initialized until it is first needed by the SomeClassSingleton consumer.
Remove the explicit private variable setting to 'null' to improve the speed slightly further ;). Anyway, it's redundant.
– nicodemus13
Mar 24 '11 at 15:27
nice point, SomeClassSingleton must be equal or lower class of SomeClass
– Fredrick Gauss
Jan 19 '13 at 9:39
what about thread safety for this singleton class?
– Rasika Perera
Aug 22 '14 at 18:23
I don't know if anyone reads old responses but i assume the private static get instance method should be public?
– Biscuit128
Aug 27 '14 at 8:03
@Biscuit128 - I do read them, and yes it should be. I updated it just in case anybody else still reads this.
– Justin Niessner
Aug 27 '14 at 14:25
|
show 1 more comment
Lazy Initialization is the concept of deferring object creation until the object is actually first used. If used properly, it can result in significant performance gains.
Personally, I've used Lazy Initialization when creating my own hand-rolled ORM in .NET 2.0. When loading my collections from the database, the actual items in the collection were lazy initialized. This meant that the collections were created quickly, but each object was loaded only when I required it.
If you're familiar with the Singleton pattern, you've probably seen lazy initialization in action as well.
public class SomeClassSingleton
{
private static SomeClass _instance = null;
private SomeClassSingleton()
{
}
public static SomeClass GetInstance()
{
if(_instance == null)
_instance = new SomeClassSingleton();
return _instance;
}
}
In this case, the instance of SomeClass is not initialized until it is first needed by the SomeClassSingleton consumer.
Remove the explicit private variable setting to 'null' to improve the speed slightly further ;). Anyway, it's redundant.
– nicodemus13
Mar 24 '11 at 15:27
nice point, SomeClassSingleton must be equal or lower class of SomeClass
– Fredrick Gauss
Jan 19 '13 at 9:39
what about thread safety for this singleton class?
– Rasika Perera
Aug 22 '14 at 18:23
I don't know if anyone reads old responses but i assume the private static get instance method should be public?
– Biscuit128
Aug 27 '14 at 8:03
@Biscuit128 - I do read them, and yes it should be. I updated it just in case anybody else still reads this.
– Justin Niessner
Aug 27 '14 at 14:25
|
show 1 more comment
Lazy Initialization is the concept of deferring object creation until the object is actually first used. If used properly, it can result in significant performance gains.
Personally, I've used Lazy Initialization when creating my own hand-rolled ORM in .NET 2.0. When loading my collections from the database, the actual items in the collection were lazy initialized. This meant that the collections were created quickly, but each object was loaded only when I required it.
If you're familiar with the Singleton pattern, you've probably seen lazy initialization in action as well.
public class SomeClassSingleton
{
private static SomeClass _instance = null;
private SomeClassSingleton()
{
}
public static SomeClass GetInstance()
{
if(_instance == null)
_instance = new SomeClassSingleton();
return _instance;
}
}
In this case, the instance of SomeClass is not initialized until it is first needed by the SomeClassSingleton consumer.
Lazy Initialization is the concept of deferring object creation until the object is actually first used. If used properly, it can result in significant performance gains.
Personally, I've used Lazy Initialization when creating my own hand-rolled ORM in .NET 2.0. When loading my collections from the database, the actual items in the collection were lazy initialized. This meant that the collections were created quickly, but each object was loaded only when I required it.
If you're familiar with the Singleton pattern, you've probably seen lazy initialization in action as well.
public class SomeClassSingleton
{
private static SomeClass _instance = null;
private SomeClassSingleton()
{
}
public static SomeClass GetInstance()
{
if(_instance == null)
_instance = new SomeClassSingleton();
return _instance;
}
}
In this case, the instance of SomeClass is not initialized until it is first needed by the SomeClassSingleton consumer.
edited Aug 27 '14 at 14:25
answered Jun 11 '09 at 0:41
Justin NiessnerJustin Niessner
209k30362494
209k30362494
Remove the explicit private variable setting to 'null' to improve the speed slightly further ;). Anyway, it's redundant.
– nicodemus13
Mar 24 '11 at 15:27
nice point, SomeClassSingleton must be equal or lower class of SomeClass
– Fredrick Gauss
Jan 19 '13 at 9:39
what about thread safety for this singleton class?
– Rasika Perera
Aug 22 '14 at 18:23
I don't know if anyone reads old responses but i assume the private static get instance method should be public?
– Biscuit128
Aug 27 '14 at 8:03
@Biscuit128 - I do read them, and yes it should be. I updated it just in case anybody else still reads this.
– Justin Niessner
Aug 27 '14 at 14:25
|
show 1 more comment
Remove the explicit private variable setting to 'null' to improve the speed slightly further ;). Anyway, it's redundant.
– nicodemus13
Mar 24 '11 at 15:27
nice point, SomeClassSingleton must be equal or lower class of SomeClass
– Fredrick Gauss
Jan 19 '13 at 9:39
what about thread safety for this singleton class?
– Rasika Perera
Aug 22 '14 at 18:23
I don't know if anyone reads old responses but i assume the private static get instance method should be public?
– Biscuit128
Aug 27 '14 at 8:03
@Biscuit128 - I do read them, and yes it should be. I updated it just in case anybody else still reads this.
– Justin Niessner
Aug 27 '14 at 14:25
Remove the explicit private variable setting to 'null' to improve the speed slightly further ;). Anyway, it's redundant.
– nicodemus13
Mar 24 '11 at 15:27
Remove the explicit private variable setting to 'null' to improve the speed slightly further ;). Anyway, it's redundant.
– nicodemus13
Mar 24 '11 at 15:27
nice point, SomeClassSingleton must be equal or lower class of SomeClass
– Fredrick Gauss
Jan 19 '13 at 9:39
nice point, SomeClassSingleton must be equal or lower class of SomeClass
– Fredrick Gauss
Jan 19 '13 at 9:39
what about thread safety for this singleton class?
– Rasika Perera
Aug 22 '14 at 18:23
what about thread safety for this singleton class?
– Rasika Perera
Aug 22 '14 at 18:23
I don't know if anyone reads old responses but i assume the private static get instance method should be public?
– Biscuit128
Aug 27 '14 at 8:03
I don't know if anyone reads old responses but i assume the private static get instance method should be public?
– Biscuit128
Aug 27 '14 at 8:03
@Biscuit128 - I do read them, and yes it should be. I updated it just in case anybody else still reads this.
– Justin Niessner
Aug 27 '14 at 14:25
@Biscuit128 - I do read them, and yes it should be. I updated it just in case anybody else still reads this.
– Justin Niessner
Aug 27 '14 at 14:25
|
show 1 more comment
In general computing terms, 'lazy evaluation' means to defer the processing on something until you actually need it. The main idea being that you can sometimes avoid costly operations if you turn out to not need it, or if the value would change before you use it.
A simple example of this is System.Exception.StackTrace. This is a string property on an exception, but it isn't actually built until you access it. Internally it does something like:
String StackTrace{
get{
if(_stackTrace==null){
_stackTrace = buildStackTrace();
}
return _stackTrace;
}
}
This saves you the overhead of actually calling buildStackTrace until someone wants to see what it is.
Properties are one way to simply provide this type of behavior.
1
This is not thread-safe.
– Cristi Diaconescu
Aug 11 '10 at 12:48
2
True, but I am not sure why you would be sharing a reference to an exception among multiple threads anyway.
– Dolphin
Aug 11 '10 at 15:36
add a comment |
In general computing terms, 'lazy evaluation' means to defer the processing on something until you actually need it. The main idea being that you can sometimes avoid costly operations if you turn out to not need it, or if the value would change before you use it.
A simple example of this is System.Exception.StackTrace. This is a string property on an exception, but it isn't actually built until you access it. Internally it does something like:
String StackTrace{
get{
if(_stackTrace==null){
_stackTrace = buildStackTrace();
}
return _stackTrace;
}
}
This saves you the overhead of actually calling buildStackTrace until someone wants to see what it is.
Properties are one way to simply provide this type of behavior.
1
This is not thread-safe.
– Cristi Diaconescu
Aug 11 '10 at 12:48
2
True, but I am not sure why you would be sharing a reference to an exception among multiple threads anyway.
– Dolphin
Aug 11 '10 at 15:36
add a comment |
In general computing terms, 'lazy evaluation' means to defer the processing on something until you actually need it. The main idea being that you can sometimes avoid costly operations if you turn out to not need it, or if the value would change before you use it.
A simple example of this is System.Exception.StackTrace. This is a string property on an exception, but it isn't actually built until you access it. Internally it does something like:
String StackTrace{
get{
if(_stackTrace==null){
_stackTrace = buildStackTrace();
}
return _stackTrace;
}
}
This saves you the overhead of actually calling buildStackTrace until someone wants to see what it is.
Properties are one way to simply provide this type of behavior.
In general computing terms, 'lazy evaluation' means to defer the processing on something until you actually need it. The main idea being that you can sometimes avoid costly operations if you turn out to not need it, or if the value would change before you use it.
A simple example of this is System.Exception.StackTrace. This is a string property on an exception, but it isn't actually built until you access it. Internally it does something like:
String StackTrace{
get{
if(_stackTrace==null){
_stackTrace = buildStackTrace();
}
return _stackTrace;
}
}
This saves you the overhead of actually calling buildStackTrace until someone wants to see what it is.
Properties are one way to simply provide this type of behavior.
answered Jun 11 '09 at 0:45
DolphinDolphin
3,74612325
3,74612325
1
This is not thread-safe.
– Cristi Diaconescu
Aug 11 '10 at 12:48
2
True, but I am not sure why you would be sharing a reference to an exception among multiple threads anyway.
– Dolphin
Aug 11 '10 at 15:36
add a comment |
1
This is not thread-safe.
– Cristi Diaconescu
Aug 11 '10 at 12:48
2
True, but I am not sure why you would be sharing a reference to an exception among multiple threads anyway.
– Dolphin
Aug 11 '10 at 15:36
1
1
This is not thread-safe.
– Cristi Diaconescu
Aug 11 '10 at 12:48
This is not thread-safe.
– Cristi Diaconescu
Aug 11 '10 at 12:48
2
2
True, but I am not sure why you would be sharing a reference to an exception among multiple threads anyway.
– Dolphin
Aug 11 '10 at 15:36
True, but I am not sure why you would be sharing a reference to an exception among multiple threads anyway.
– Dolphin
Aug 11 '10 at 15:36
add a comment |
Here you can read about Lazy Initialization with sample code.
When you have an object that is
expensive to create, and the program
might not use it. For example, assume
that you have in memory a Customer
object that has an Orders property
that contains a large array of Order
objects that, to be initialized,
requires a database connection. If the
user never asks to display the Orders
or use the data in a computation, then
there is no reason to use system
memory or computing cycles to create
it. By using Lazy to declare
the Orders object for lazy
initialization, you can avoid wasting
system resources when the object is
not used.
When you have an object that is
expensive to create, and you want to
defer its creation until after other
expensive operations have been
completed. For example, assume that
your program loads several object
instances when it starts, but only
some of them are required immediately.
You can improve the startup
performance of the program by
deferring initialization of the
objects that are not required until
the required objects have been
created.
add a comment |
Here you can read about Lazy Initialization with sample code.
When you have an object that is
expensive to create, and the program
might not use it. For example, assume
that you have in memory a Customer
object that has an Orders property
that contains a large array of Order
objects that, to be initialized,
requires a database connection. If the
user never asks to display the Orders
or use the data in a computation, then
there is no reason to use system
memory or computing cycles to create
it. By using Lazy to declare
the Orders object for lazy
initialization, you can avoid wasting
system resources when the object is
not used.
When you have an object that is
expensive to create, and you want to
defer its creation until after other
expensive operations have been
completed. For example, assume that
your program loads several object
instances when it starts, but only
some of them are required immediately.
You can improve the startup
performance of the program by
deferring initialization of the
objects that are not required until
the required objects have been
created.
add a comment |
Here you can read about Lazy Initialization with sample code.
When you have an object that is
expensive to create, and the program
might not use it. For example, assume
that you have in memory a Customer
object that has an Orders property
that contains a large array of Order
objects that, to be initialized,
requires a database connection. If the
user never asks to display the Orders
or use the data in a computation, then
there is no reason to use system
memory or computing cycles to create
it. By using Lazy to declare
the Orders object for lazy
initialization, you can avoid wasting
system resources when the object is
not used.
When you have an object that is
expensive to create, and you want to
defer its creation until after other
expensive operations have been
completed. For example, assume that
your program loads several object
instances when it starts, but only
some of them are required immediately.
You can improve the startup
performance of the program by
deferring initialization of the
objects that are not required until
the required objects have been
created.
Here you can read about Lazy Initialization with sample code.
When you have an object that is
expensive to create, and the program
might not use it. For example, assume
that you have in memory a Customer
object that has an Orders property
that contains a large array of Order
objects that, to be initialized,
requires a database connection. If the
user never asks to display the Orders
or use the data in a computation, then
there is no reason to use system
memory or computing cycles to create
it. By using Lazy to declare
the Orders object for lazy
initialization, you can avoid wasting
system resources when the object is
not used.
When you have an object that is
expensive to create, and you want to
defer its creation until after other
expensive operations have been
completed. For example, assume that
your program loads several object
instances when it starts, but only
some of them are required immediately.
You can improve the startup
performance of the program by
deferring initialization of the
objects that are not required until
the required objects have been
created.
answered Nov 5 '10 at 14:24
Amir RezaeiAmir Rezaei
2,17452445
2,17452445
add a comment |
add a comment |
Lazy initialization of an object means that its creation is deferred until it is first used. (For this topic, the terms lazy initialization and lazy instantiation are synonymous.) Lazy initialization is primarily used to improve performance, avoid wasteful computation, and reduce program memory requirements. These are the most common scenarios:
When you have an object that is expensive to create, and the program might not use it. For example, assume that you have in memory a Customer object that has an Orders property that contains a large array of Order objects that, to be initialized, requires a database connection. If the user never asks to display the Orders or use the data in a computation, then there is no reason to use system memory or computing cycles to create it. By using Lazy to declare the Orders object for lazy initialization, you can avoid wasting system resources when the object is not used.
When you have an object that is expensive to create, and you want to defer its creation until after other expensive operations have been completed. For example, assume that your program loads several object instances when it starts, but only some of them are required immediately. You can improve the startup performance of the program by deferring initialization of the objects that are not required until the required objects have been created.
Although you can write your own code to perform lazy initialization, we recommend that you use Lazy instead. Lazy and its related types also support thread-safety and provide a consistent exception propagation policy.
add a comment |
Lazy initialization of an object means that its creation is deferred until it is first used. (For this topic, the terms lazy initialization and lazy instantiation are synonymous.) Lazy initialization is primarily used to improve performance, avoid wasteful computation, and reduce program memory requirements. These are the most common scenarios:
When you have an object that is expensive to create, and the program might not use it. For example, assume that you have in memory a Customer object that has an Orders property that contains a large array of Order objects that, to be initialized, requires a database connection. If the user never asks to display the Orders or use the data in a computation, then there is no reason to use system memory or computing cycles to create it. By using Lazy to declare the Orders object for lazy initialization, you can avoid wasting system resources when the object is not used.
When you have an object that is expensive to create, and you want to defer its creation until after other expensive operations have been completed. For example, assume that your program loads several object instances when it starts, but only some of them are required immediately. You can improve the startup performance of the program by deferring initialization of the objects that are not required until the required objects have been created.
Although you can write your own code to perform lazy initialization, we recommend that you use Lazy instead. Lazy and its related types also support thread-safety and provide a consistent exception propagation policy.
add a comment |
Lazy initialization of an object means that its creation is deferred until it is first used. (For this topic, the terms lazy initialization and lazy instantiation are synonymous.) Lazy initialization is primarily used to improve performance, avoid wasteful computation, and reduce program memory requirements. These are the most common scenarios:
When you have an object that is expensive to create, and the program might not use it. For example, assume that you have in memory a Customer object that has an Orders property that contains a large array of Order objects that, to be initialized, requires a database connection. If the user never asks to display the Orders or use the data in a computation, then there is no reason to use system memory or computing cycles to create it. By using Lazy to declare the Orders object for lazy initialization, you can avoid wasting system resources when the object is not used.
When you have an object that is expensive to create, and you want to defer its creation until after other expensive operations have been completed. For example, assume that your program loads several object instances when it starts, but only some of them are required immediately. You can improve the startup performance of the program by deferring initialization of the objects that are not required until the required objects have been created.
Although you can write your own code to perform lazy initialization, we recommend that you use Lazy instead. Lazy and its related types also support thread-safety and provide a consistent exception propagation policy.
Lazy initialization of an object means that its creation is deferred until it is first used. (For this topic, the terms lazy initialization and lazy instantiation are synonymous.) Lazy initialization is primarily used to improve performance, avoid wasteful computation, and reduce program memory requirements. These are the most common scenarios:
When you have an object that is expensive to create, and the program might not use it. For example, assume that you have in memory a Customer object that has an Orders property that contains a large array of Order objects that, to be initialized, requires a database connection. If the user never asks to display the Orders or use the data in a computation, then there is no reason to use system memory or computing cycles to create it. By using Lazy to declare the Orders object for lazy initialization, you can avoid wasting system resources when the object is not used.
When you have an object that is expensive to create, and you want to defer its creation until after other expensive operations have been completed. For example, assume that your program loads several object instances when it starts, but only some of them are required immediately. You can improve the startup performance of the program by deferring initialization of the objects that are not required until the required objects have been created.
Although you can write your own code to perform lazy initialization, we recommend that you use Lazy instead. Lazy and its related types also support thread-safety and provide a consistent exception propagation policy.
answered May 24 '11 at 13:24
Rakesh KumarRakesh Kumar
291
291
add a comment |
add a comment |
//Lazy instantiation delays certain tasks.
//It typically improves the startup time of a C# application.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LazyLoad
{
class Program
{
static void Main(string args)
{
Lazy<MyClass> MyLazyClass = new Lazy<MyClass>(); // create lazy class
Console.WriteLine("IsValueCreated = {0}",MyLazyClass.IsValueCreated); // print value to check if initialization is over
MyClass sample = MyLazyClass.Value; // real value Creation Time
Console.WriteLine("Length = {0}", sample.Length); // print array length
Console.WriteLine("IsValueCreated = {0}", MyLazyClass.IsValueCreated); // print value to check if initialization is over
Console.ReadLine();
}
}
class MyClass
{
int array;
public MyClass()
{
array = new int[10];
}
public int Length
{
get
{
return this.array.Length;
}
}
}
}
// out put
// IsValueCreated = False
// Length = 10
// IsValueCreated = True
add a comment |
//Lazy instantiation delays certain tasks.
//It typically improves the startup time of a C# application.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LazyLoad
{
class Program
{
static void Main(string args)
{
Lazy<MyClass> MyLazyClass = new Lazy<MyClass>(); // create lazy class
Console.WriteLine("IsValueCreated = {0}",MyLazyClass.IsValueCreated); // print value to check if initialization is over
MyClass sample = MyLazyClass.Value; // real value Creation Time
Console.WriteLine("Length = {0}", sample.Length); // print array length
Console.WriteLine("IsValueCreated = {0}", MyLazyClass.IsValueCreated); // print value to check if initialization is over
Console.ReadLine();
}
}
class MyClass
{
int array;
public MyClass()
{
array = new int[10];
}
public int Length
{
get
{
return this.array.Length;
}
}
}
}
// out put
// IsValueCreated = False
// Length = 10
// IsValueCreated = True
add a comment |
//Lazy instantiation delays certain tasks.
//It typically improves the startup time of a C# application.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LazyLoad
{
class Program
{
static void Main(string args)
{
Lazy<MyClass> MyLazyClass = new Lazy<MyClass>(); // create lazy class
Console.WriteLine("IsValueCreated = {0}",MyLazyClass.IsValueCreated); // print value to check if initialization is over
MyClass sample = MyLazyClass.Value; // real value Creation Time
Console.WriteLine("Length = {0}", sample.Length); // print array length
Console.WriteLine("IsValueCreated = {0}", MyLazyClass.IsValueCreated); // print value to check if initialization is over
Console.ReadLine();
}
}
class MyClass
{
int array;
public MyClass()
{
array = new int[10];
}
public int Length
{
get
{
return this.array.Length;
}
}
}
}
// out put
// IsValueCreated = False
// Length = 10
// IsValueCreated = True
//Lazy instantiation delays certain tasks.
//It typically improves the startup time of a C# application.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LazyLoad
{
class Program
{
static void Main(string args)
{
Lazy<MyClass> MyLazyClass = new Lazy<MyClass>(); // create lazy class
Console.WriteLine("IsValueCreated = {0}",MyLazyClass.IsValueCreated); // print value to check if initialization is over
MyClass sample = MyLazyClass.Value; // real value Creation Time
Console.WriteLine("Length = {0}", sample.Length); // print array length
Console.WriteLine("IsValueCreated = {0}", MyLazyClass.IsValueCreated); // print value to check if initialization is over
Console.ReadLine();
}
}
class MyClass
{
int array;
public MyClass()
{
array = new int[10];
}
public int Length
{
get
{
return this.array.Length;
}
}
}
}
// out put
// IsValueCreated = False
// Length = 10
// IsValueCreated = True
answered Jan 5 '14 at 5:34
Karthik Krishna BaijuKarthik Krishna Baiju
43459
43459
add a comment |
add a comment |
As what I have understood about lazy init so far, is that the program does not load/request all data a once. It waits for the use of it before requesting it from eg. a SQL-server.
If you have a database with a large table joined with a large amount of subtables and you dont require the details joined from the other tabels unless going into "edit" or "view details", then Lazy Init. will help the application to go faster and first "lazy load" the detailsdata upon needed.
In SQL or LINQ you can set this "setting" on your database model pr. dataelement.
Hope this makes any sense to your question?
A webclient (eg. a browser) does the same thing. The images are "lazy loaded" after the HTML and AJAX is also a "sort of lazy init" if used right.
add a comment |
As what I have understood about lazy init so far, is that the program does not load/request all data a once. It waits for the use of it before requesting it from eg. a SQL-server.
If you have a database with a large table joined with a large amount of subtables and you dont require the details joined from the other tabels unless going into "edit" or "view details", then Lazy Init. will help the application to go faster and first "lazy load" the detailsdata upon needed.
In SQL or LINQ you can set this "setting" on your database model pr. dataelement.
Hope this makes any sense to your question?
A webclient (eg. a browser) does the same thing. The images are "lazy loaded" after the HTML and AJAX is also a "sort of lazy init" if used right.
add a comment |
As what I have understood about lazy init so far, is that the program does not load/request all data a once. It waits for the use of it before requesting it from eg. a SQL-server.
If you have a database with a large table joined with a large amount of subtables and you dont require the details joined from the other tabels unless going into "edit" or "view details", then Lazy Init. will help the application to go faster and first "lazy load" the detailsdata upon needed.
In SQL or LINQ you can set this "setting" on your database model pr. dataelement.
Hope this makes any sense to your question?
A webclient (eg. a browser) does the same thing. The images are "lazy loaded" after the HTML and AJAX is also a "sort of lazy init" if used right.
As what I have understood about lazy init so far, is that the program does not load/request all data a once. It waits for the use of it before requesting it from eg. a SQL-server.
If you have a database with a large table joined with a large amount of subtables and you dont require the details joined from the other tabels unless going into "edit" or "view details", then Lazy Init. will help the application to go faster and first "lazy load" the detailsdata upon needed.
In SQL or LINQ you can set this "setting" on your database model pr. dataelement.
Hope this makes any sense to your question?
A webclient (eg. a browser) does the same thing. The images are "lazy loaded" after the HTML and AJAX is also a "sort of lazy init" if used right.
answered Jun 11 '09 at 0:29
BerggreenDKBerggreenDK
3,42993054
3,42993054
add a comment |
add a comment |
The database examples that have been mentioned so far are good, but it's not restricted to just the data access layer. You could apply the same principles to any situation where performance or memory can be a concern. A good example (although not .NET) is in Cocoa, where you can wait until the user requests a window to actually load it (and its associated objects) from the nib. This can help keep memory usage down and speed up the initial application load, especially when you're talking about things like Preferences windows that won't be needed until some later time, if ever.
add a comment |
The database examples that have been mentioned so far are good, but it's not restricted to just the data access layer. You could apply the same principles to any situation where performance or memory can be a concern. A good example (although not .NET) is in Cocoa, where you can wait until the user requests a window to actually load it (and its associated objects) from the nib. This can help keep memory usage down and speed up the initial application load, especially when you're talking about things like Preferences windows that won't be needed until some later time, if ever.
add a comment |
The database examples that have been mentioned so far are good, but it's not restricted to just the data access layer. You could apply the same principles to any situation where performance or memory can be a concern. A good example (although not .NET) is in Cocoa, where you can wait until the user requests a window to actually load it (and its associated objects) from the nib. This can help keep memory usage down and speed up the initial application load, especially when you're talking about things like Preferences windows that won't be needed until some later time, if ever.
The database examples that have been mentioned so far are good, but it's not restricted to just the data access layer. You could apply the same principles to any situation where performance or memory can be a concern. A good example (although not .NET) is in Cocoa, where you can wait until the user requests a window to actually load it (and its associated objects) from the nib. This can help keep memory usage down and speed up the initial application load, especially when you're talking about things like Preferences windows that won't be needed until some later time, if ever.
answered Jun 11 '09 at 0:44
Marc CharbonneauMarc Charbonneau
38.7k37081
38.7k37081
add a comment |
add a comment |
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