Agfdhyk

I believe this question is similar to this one but the terminology is different. From the Mongoose 4 documentation:

We may also define our own custom document instance methods too.

// define a schema

var animalSchema = new Schema({ name: String, type: String });



// assign a function to the "methods" object of our animalSchema

animalSchema.methods.findSimilarTypes = function (cb) {

  return this.model('Animal').find({ type: this.type }, cb);

}

Now all of our animal instances have a findSimilarTypes method available to it.

And then:

Adding static methods to a Model is simple as well. Continuing with our animalSchema:

// assign a function to the "statics" object of our animalSchema

animalSchema.statics.findByName = function (name, cb) {

  return this.find({ name: new RegExp(name, 'i') }, cb);

}



var Animal = mongoose.model('Animal', animalSchema);

Animal.findByName('fido', function (err, animals) {

  console.log(animals);

});

It seems with static methods each of the animal instances would have the findByName method available to it as well. What are the statics and methods objects in a Schema? What is the difference and why would I use one over the other?

statics are the methods defined on the Model. methods are defined on the document (instance).

You might do

Animal.findByName('fido', function(err, fido){

    // fido => { name: 'fido', type: 'dog' }

});

And then you might use the document instance fido to do

fido.findSimilarTypes(function(err, dogs){

    // dogs => [ {name:'fido',type:'dog} , {name:'sheeba',type:'dog'} ]

});

Database logic should be encapsulated within the data model. Mongoose provides 2 ways of doing this, methods and statics. Methods adds an instance method to documents whereas Statics adds static “class” methods to the Models itself.The static keyword defines a static method for a model. Static methods aren't called on instances of the model. Instead, they're called on the model itself. These are often utility functions, such as functions to create or clone objects. like example below:

const bookSchema = mongoose.Schema({

  title: {

    type : String,

    required : [true, 'Book name required']

  },

  publisher : {

    type : String,

    required : [true, 'Publisher name required']

  },

  thumbnail : {

    type : String

  }

  type : {

    type : String

  },

  hasAward : {

    type : Boolean

  }

});



//method

bookSchema.methods.findByType = function (callback) {

  return this.model('Book').find({ type: this.type }, callback);

};



// statics

bookSchema.statics.findBooksWithAward = function (callback) {

  Book.find({ hasAward: true }, callback);

};



const Book = mongoose.model('Book', bookSchema);

export default Book;

for more info: https://osmangoni.info/posts/separating-methods-schema-statics-mongoose/