Backbone.js get and set nested object attribute

Question

I have a simple question about Backbone.js' get and set functions.

1) With the code below, how can I 'get' or 'set' obj1.myAttribute1 directly?

Another question:

2) In the Model, aside from the defaults object, where can/should I declare my model's other attributes, such that they can be accessed via Backbone's get and set methods?

var MyModel = Backbone.Model.extend({
    defaults: {
        obj1 : {
            "myAttribute1" : false,
            "myAttribute2" : true,
        }
    }
})

var MyView = Backbone.View.extend({
    myFunc: function(){
        console.log(this.model.get("obj1"));
        //returns the obj1 object
        //but how do I get obj1.myAttribute1 directly so that it returns false?
    }
});

I know I can do:

this.model.get("obj1").myAttribute1;

but is that good practice?

Answer 1

Solution proposed by Domenic has some drawbacks. Say you want to listen to 'change' event. In that case 'initialize' method will not be fired and your custom value for attribute will be replaced with json object from server. In my project I faced with this problem. My solution to override 'set' method of Model:

set: function(key, val, options) {
    if (typeof key === 'object') {
        var attrs = key;
        attrs.content = new module.BaseItem(attrs.content || {});
        attrs.children = new module.MenuItems(attrs.children || []);
    }

    return Backbone.Model.prototype.set.call(this, key, val, options);
}, 

Answer 2

I created backbone-deep-model for this - just extend Backbone.DeepModel instead of Backbone.Model and you can then use paths to get/set nested model attributes. It maintains change events too.

model.bind('change:user.name.first', function(){...});
model.set({'user.name.first': 'Eric'});
model.get('user.name.first'); //Eric

Answer 3

I had the same problem @pagewil and @Benno had with @Domenic's solution. My answer was to instead write a simple sub-class of Backbone.Model that fixes the problem.

// Special model implementation that allows you to easily nest Backbone models as properties.
Backbone.NestedModel = Backbone.Model.extend({
    // Define Backbone models that are present in properties
    // Expected Format:
    // [{key: 'courses', model: Course}]
    models: [],

    set: function(key, value, options) {
        var attrs, attr, val;

        if (_.isObject(key) || key == null) {
            attrs = key;
            options = value;
        } else {
            attrs = {};
            attrs[key] = value;
        }

        _.each(this.models, function(item){
            if (_.isObject(attrs[item.key])) {
                attrs[item.key] = new item.model(attrs[item.key]);
            }
        },this);

        return Backbone.Model.prototype.set.call(this, attrs, options);
    }
});

var Obj = Backbone.Model.extend({
    defaults: {
        myAttribute1: false,
        myAttribute2: true
    }
});

var MyModel = Backbone.NestedModel.extend({
    defaults: {
        obj1: new Obj()
    },

    models: [{key: 'obj1', model: Obj}]
});

What NestedModel does for you is allow these to work (which is what happens when myModel gets set via JSON data):

var myModel = new MyModel();
myModel.set({ obj1: { myAttribute1: 'abc', myAttribute2: 'xyz' } });
myModel.set('obj1', { myAttribute1: 123, myAttribute2: 456 });

It would be easy to generate the models list automatically in initialize, but this solution was good enough for me.

Answer 4

Domenic's solution will work however each new MyModel will point to the same instance of Obj. To avoid this, MyModel should look like:

var MyModel = Backbone.Model.extend({
  initialize: function() {
     myDefaults = {
       obj1: new Obj()
     } 
     this.set(myDefaults);
  }
});

See c3rin's answer @ https://stackoverflow.com/a/6364480/1072653 for a full explanation.

Answer 5

While in some cases using Backbone models instead of nested Object attributes makes sense as Domenic mentioned, in simpler cases you could create a setter function in the model:

var MyModel = Backbone.Model.extend({
    defaults: {
        obj1 : {
            "myAttribute1" : false,
            "myAttribute2" : true,
        }
    },
    setObj1Attribute: function(name, value) {
        var obj1 = this.get('obj1');
        obj1[name] = value;
        this.set('obj1', obj1);
    }
})

Answer 6

If you interact with backend, which requires object with nesting structure. But with backbone more easy to work with linear structure.

backbone.linear can help you.