Backbone.Model.extend不会创建实例属性

Question

I am new to Backbone and JS, so correct me if I am wrong...

Using the example from backbone.js site,

var Note = Backbone.Model.extend({
    initialize: function() { ... },
    author: function() { ... },
    coordinates: function() { ... },
    allowedToEdit: function(account) {
        return true;
    } 
});

Backbone.js says,

"To create a Model class of your own, you extend Backbone.Model and provide instance properties, as >well as optional classProperties to be attached directly to the constructor function."

So i create two objects,

var n1 = new Note;
var n2 = new Note;

Now the properties autor, allowedToEdit coordinates etc., are not instance properties of n1 and n2. They are created under the proto link. How do I create instance properties in backbone.js

Also, if I try to modify a inherited property in javascript in an object, the inherited property is not changed. Instead, a new property with the same name is created in the objects instance properties. How do I achive this? Thanks in advance...

Answer 1

I believe you are a bit confused about what extend does. Extend is analogous to inheritance. If you extend the Model in this way, you create a derived "class" called Note which now has these member functions.

But that is not what you want, I don't think. You want a model with these DATA properties. Adding data to an instance is simple:

var Note = Backbone.Model.extend({});
var n1 = new Note({
    author: "Gautham",
    coordinates: {x: 200, y: 100},
    allowedToEdit: true
});

var author = n1.get("author");

In other words, data properties on Backbone models are dynamic. You don't need to declare them in your Note derivation.

If, however, you would like the Note derivation to have properties that look this way, you can always define them to proxy through to the get function:

var Note = Backbone.Model.extend({
    author: function() { return this.get('author'); },
    coordinates: function() { return this.get('coordinates'); }
    allowedToEdit: function() { return this.get('allowedToEdit'); }
});
var n1 = new Note({...});
var author = n1.author();

Answer 2

You wanted to use defaults attribute, that are the behavior that you are expecting:

var Note = Backbone.Model.extend({
  defaults:function(){
    return {
      author : 'Default author',
      coordinates : [0,0],
    };
  }
});

var note1 = new Note;
var note2 = new Note;
var note3 = new Note({author: 'Daniel!', coordinates:[9,9]});

console.log( note1.toJSON() );
console.log( note2.toJSON() );
console.log( note3.toJSON() );