Bob Martin: “C has perfect encapsulation” HOW?
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Bob Martin in this video says that "C has perfect encapsulation". I do not understand why he is saying this... I understand that we can separate the implementation in a .c file and declare the interface in a header .h file, but there is nothing really stopping me from accessing implementation details like this:
main.c
#include <stdio.h>
#include "file1.h"
extern int x;
int main() {
printf("%dn", x);
return 0;
}
file1.c
int x = 5;
int getnum_file1() {
return x + 1;
}
file1.h
int getnum_file1();
In this case, main.c has access to implementation detail in file1.c. This code also compiles and executes with the expected result. How is this perfect encapsulation??
c oop encapsulation software-design
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
|
show 1 more comment
Bob Martin in this video says that "C has perfect encapsulation". I do not understand why he is saying this... I understand that we can separate the implementation in a .c file and declare the interface in a header .h file, but there is nothing really stopping me from accessing implementation details like this:
main.c
#include <stdio.h>
#include "file1.h"
extern int x;
int main() {
printf("%dn", x);
return 0;
}
file1.c
int x = 5;
int getnum_file1() {
return x + 1;
}
file1.h
int getnum_file1();
In this case, main.c has access to implementation detail in file1.c. This code also compiles and executes with the expected result. How is this perfect encapsulation??
c oop encapsulation software-design
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
Just because a language has encapsulation facilities doesn't mean a programmer can't fail to encapsulate.
– StoryTeller
Nov 22 '18 at 8:47
Because file1 is breaking encapsulation by defining a (potential) global variable?
– GermanNerd
Nov 22 '18 at 8:48
c and c++ can be used and abused its really up to the developer to employ good practice. You can do really nasty things in both languages, even Java lets you do some pretty awful things, for example its perfectly possible to define a static public member variable which is globally accessible. In your example, remove extern int x, changed x in file1.c to be static.
– SPlatten
Nov 22 '18 at 8:49
Ah I see.. so is the best practice to attach the 'static' keyword to any variable you would like to keep hidden as implementation detail?
– N. Parikh
Nov 22 '18 at 8:56
@N.Parikh, static just restricts the variable to the scope it is declared in.
– SPlatten
Nov 22 '18 at 9:02
|
show 1 more comment
Bob Martin in this video says that "C has perfect encapsulation". I do not understand why he is saying this... I understand that we can separate the implementation in a .c file and declare the interface in a header .h file, but there is nothing really stopping me from accessing implementation details like this:
main.c
#include <stdio.h>
#include "file1.h"
extern int x;
int main() {
printf("%dn", x);
return 0;
}
file1.c
int x = 5;
int getnum_file1() {
return x + 1;
}
file1.h
int getnum_file1();
In this case, main.c has access to implementation detail in file1.c. This code also compiles and executes with the expected result. How is this perfect encapsulation??
c oop encapsulation software-design
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
Bob Martin in this video says that "C has perfect encapsulation". I do not understand why he is saying this... I understand that we can separate the implementation in a .c file and declare the interface in a header .h file, but there is nothing really stopping me from accessing implementation details like this:
main.c
#include <stdio.h>
#include "file1.h"
extern int x;
int main() {
printf("%dn", x);
return 0;
}
file1.c
int x = 5;
int getnum_file1() {
return x + 1;
}
file1.h
int getnum_file1();
In this case, main.c has access to implementation detail in file1.c. This code also compiles and executes with the expected result. How is this perfect encapsulation??
c oop encapsulation software-design
c oop encapsulation software-design
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
asked Nov 22 '18 at 8:45
N. ParikhN. Parikh
555
555
Just because a language has encapsulation facilities doesn't mean a programmer can't fail to encapsulate.
– StoryTeller
Nov 22 '18 at 8:47
Because file1 is breaking encapsulation by defining a (potential) global variable?
– GermanNerd
Nov 22 '18 at 8:48
c and c++ can be used and abused its really up to the developer to employ good practice. You can do really nasty things in both languages, even Java lets you do some pretty awful things, for example its perfectly possible to define a static public member variable which is globally accessible. In your example, remove extern int x, changed x in file1.c to be static.
– SPlatten
Nov 22 '18 at 8:49
Ah I see.. so is the best practice to attach the 'static' keyword to any variable you would like to keep hidden as implementation detail?
– N. Parikh
Nov 22 '18 at 8:56
@N.Parikh, static just restricts the variable to the scope it is declared in.
– SPlatten
Nov 22 '18 at 9:02
|
show 1 more comment
Just because a language has encapsulation facilities doesn't mean a programmer can't fail to encapsulate.
– StoryTeller
Nov 22 '18 at 8:47
Because file1 is breaking encapsulation by defining a (potential) global variable?
– GermanNerd
Nov 22 '18 at 8:48
c and c++ can be used and abused its really up to the developer to employ good practice. You can do really nasty things in both languages, even Java lets you do some pretty awful things, for example its perfectly possible to define a static public member variable which is globally accessible. In your example, remove extern int x, changed x in file1.c to be static.
– SPlatten
Nov 22 '18 at 8:49
Ah I see.. so is the best practice to attach the 'static' keyword to any variable you would like to keep hidden as implementation detail?
– N. Parikh
Nov 22 '18 at 8:56
@N.Parikh, static just restricts the variable to the scope it is declared in.
– SPlatten
Nov 22 '18 at 9:02
Just because a language has encapsulation facilities doesn't mean a programmer can't fail to encapsulate.
– StoryTeller
Nov 22 '18 at 8:47
Just because a language has encapsulation facilities doesn't mean a programmer can't fail to encapsulate.
– StoryTeller
Nov 22 '18 at 8:47
Because file1 is breaking encapsulation by defining a (potential) global variable?
– GermanNerd
Nov 22 '18 at 8:48
Because file1 is breaking encapsulation by defining a (potential) global variable?
– GermanNerd
Nov 22 '18 at 8:48
c and c++ can be used and abused its really up to the developer to employ good practice. You can do really nasty things in both languages, even Java lets you do some pretty awful things, for example its perfectly possible to define a static public member variable which is globally accessible. In your example, remove extern int x, changed x in file1.c to be static.
– SPlatten
Nov 22 '18 at 8:49
c and c++ can be used and abused its really up to the developer to employ good practice. You can do really nasty things in both languages, even Java lets you do some pretty awful things, for example its perfectly possible to define a static public member variable which is globally accessible. In your example, remove extern int x, changed x in file1.c to be static.
– SPlatten
Nov 22 '18 at 8:49
Ah I see.. so is the best practice to attach the 'static' keyword to any variable you would like to keep hidden as implementation detail?
– N. Parikh
Nov 22 '18 at 8:56
Ah I see.. so is the best practice to attach the 'static' keyword to any variable you would like to keep hidden as implementation detail?
– N. Parikh
Nov 22 '18 at 8:56
@N.Parikh, static just restricts the variable to the scope it is declared in.
– SPlatten
Nov 22 '18 at 9:02
@N.Parikh, static just restricts the variable to the scope it is declared in.
– SPlatten
Nov 22 '18 at 9:02
|
show 1 more comment
1 Answer
1
active
oldest
votes
A way to ensure the encapsulation is declaring x as static int x = 5;, so it won't be visible from an external object (even using extern).
Obviously, a global variable as x is, can be accessed from another object (via linker, through the extern you have added). However, this usually leads to a "spaghetti" code, in which variables are accessed and/or modified from wherever because there is not a proper encapsulation (and C or C++ do provide useful ways to avoid that).
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
answered Nov 22 '18 at 8:55
JoseJose
1,291516
add a comment |
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oldest
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votes
A way to ensure the encapsulation is declaring x as static int x = 5;, so it won't be visible from an external object (even using extern).
Obviously, a global variable as x is, can be accessed from another object (via linker, through the extern you have added). However, this usually leads to a "spaghetti" code, in which variables are accessed and/or modified from wherever because there is not a proper encapsulation (and C or C++ do provide useful ways to avoid that).
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
answered Nov 22 '18 at 8:55
JoseJose
1,291516
add a comment |
A way to ensure the encapsulation is declaring x as static int x = 5;, so it won't be visible from an external object (even using extern).
Obviously, a global variable as x is, can be accessed from another object (via linker, through the extern you have added). However, this usually leads to a "spaghetti" code, in which variables are accessed and/or modified from wherever because there is not a proper encapsulation (and C or C++ do provide useful ways to avoid that).
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
answered Nov 22 '18 at 8:55
JoseJose
1,291516
add a comment |
A way to ensure the encapsulation is declaring x as static int x = 5;, so it won't be visible from an external object (even using extern).
Obviously, a global variable as x is, can be accessed from another object (via linker, through the extern you have added). However, this usually leads to a "spaghetti" code, in which variables are accessed and/or modified from wherever because there is not a proper encapsulation (and C or C++ do provide useful ways to avoid that).
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
answered Nov 22 '18 at 8:55
JoseJose
1,291516
A way to ensure the encapsulation is declaring x as static int x = 5;, so it won't be visible from an external object (even using extern).
Obviously, a global variable as x is, can be accessed from another object (via linker, through the extern you have added). However, this usually leads to a "spaghetti" code, in which variables are accessed and/or modified from wherever because there is not a proper encapsulation (and C or C++ do provide useful ways to avoid that).
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
answered Nov 22 '18 at 8:55
JoseJose
1,291516
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
edited Nov 22 '18 at 9:22
Toby Speight
17.6k134469
17.6k134469
answered Nov 22 '18 at 8:55
JoseJose
1,291516
answered Nov 22 '18 at 8:55
JoseJose
1,291516
answered Nov 22 '18 at 8:55
JoseJose
1,291516
1,291516
add a comment |
add a comment |
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Just because a language has encapsulation facilities doesn't mean a programmer can't fail to encapsulate.
– StoryTeller
Nov 22 '18 at 8:47
Because file1 is breaking encapsulation by defining a (potential) global variable?
– GermanNerd
Nov 22 '18 at 8:48
c and c++ can be used and abused its really up to the developer to employ good practice. You can do really nasty things in both languages, even Java lets you do some pretty awful things, for example its perfectly possible to define a static public member variable which is globally accessible. In your example, remove extern int x, changed x in file1.c to be static.
– SPlatten
Nov 22 '18 at 8:49
Ah I see.. so is the best practice to attach the 'static' keyword to any variable you would like to keep hidden as implementation detail?
– N. Parikh
Nov 22 '18 at 8:56
@N.Parikh, static just restricts the variable to the scope it is declared in.
– SPlatten
Nov 22 '18 at 9:02