如何从backbone.js中的集合调用模型的方法？

Question

I've been trying to learn backbone.js these days. What I've is a model and a collection. The model has some default properties defined in it which I want to fetch within a collection. This is my code:

var model = Backbone.Model.extend({
    defaults : {
        done : true
    }
});

var collection = Backbone.Collection.extend({
    model : model,  

    pickMe : function () {
        log(this.model.get('done')); //return undefined
    }   
});

var col = new collection();
col.pickMe();

How do I call methods defined in my model from collection? Am I doing wrong here?

Answer 1

The basic setup of Backbone is this :

You have models which are part of collection(s). So here in your setup you have a model constructor model and collection constructor collection , but you have no models in your collection and if you have any models they will be an array, so your code should be something like this

var model = Backbone.Model.extend({
    defaults : {
        done : true
    }
});

var collection = Backbone.Collection.extend({
    model : model,  

    pickMe : function () {
        for ( i = 0; i < this.models.length; i++ ) {
            log(this.models[i].get('done')); // this prints 'true'
        }
    }   
});

// Here we are actually creating a new model for the collection
var col = new collection([{ name : 'jack' }]); 

col.pickMe();

You can check the working jsFiddle here : http://jsfiddle.net/S8tHk/1/

Answer 2

@erturne is correct, you're trying to call a method on your model constructor, not a model instance. That doesn't make sense.

If you really want to define methods on the collection, then @drinchev provides an example of how to iterate through the models in the collection and invoke their methods. Although, the example is rather clunky -- using the built-in iterator methods would be more elegant.

Depending what you're trying to accomplish, you may want to just use the built-in collection iterator methods to invoke methods on each model instead of defining methods on the collection. Eg:

var Model = Backbone.Model.extend({
    defaults : {
      done : true
    }
});

var Collection = Backbone.Collection.extend({
    model : Model
});

var col = new Collection([{}, {done : false}, {}]);

col.each(function (model) {
  log(model.get('done'));
});

Answer 3

I think you'd better attach your model methods to the model itself, not in the collection. So you should have somethings like this:

var model = Backbone.Model.extend({
    defaults : {
        done : true
    },
    pickMe : function () {
        log(this.get('done'));
    }
});

var collection = Backbone.Collection.extend({
    model : model,  
});


var model = collection.get(id)
model.pickMe()