Collection.get returning undefined in backbone.js

I have issue with collection.get and model.get returning undefined.

here is my initializecode

initialize: function () {
    this.collection = new productsCollection();
    this.model = new productModel();
}

here is my render code

this.collection.fetch({
    success: function (product) {
        console.log(product);
        $(that.el).html(_.template(productListTemplate, { products: product.models, _: _ }));
    }
});

my list of products is displaying fine. when i click on each product i get a popup where name can be changed

i want to get the set new name in the model and trigger save

but i am unable to get the model of the product here is the code

$("#productName").val($(e.currentTarget).html());

var ID = $(e.currentTarget).data("id");
var item = this.collection.get(ID);

console.log("start..........");
console.log(item);
console.log(ID)
//            console.log(this.collection);
console.log(this.model.get(item));
console.log("end..........");

$('.modal').modal('toggle');

I am able to get the correct id in console but not collections and models

can some one help thanks in advance

UPDATE here is the complete view code

function ($, _, Backbone, popupModal, productTab, productsCollection, productListTemplate, productModel) {
    var productListView = Backbone.View.extend({
        el: $("#page"),
        initialize: function () {
            this.collection = new productsCollection();
            this.model = new productModel();
            this.model.bind('change', this.loadResults, this);
        },
        render: function () {
            this.loadResults();
        },
        loadResults: function () {
            var that = this;
            this.collection.fetch({
                success: function (product) {
                    console.log(product);
                    $(that.el).html(_.template(productListTemplate, { products: product.models, _: _ }));
                }
            });
            var modalWindow = $(".modal").modal({
                show: false,
                backdrop: true,
                closeOnEscape: true
            });
            $('#createProduct').click(function (e) {
                this.modalWindow.modal('show');
            });
        },
        // This will simply listen for scroll events on the current el
        events: {
            "click #saveProduct": "saveProduct",
            "click .productTabs": "productTabs",
            "click .productDetails": "productDetails"
        },
        saveProduct: function () {
            this.model.set({
                Name: $('#productName').val()
            });
            this.model.save({ id: this.model.get('id') },
         {
             success: function (model, response) {
                 //                 console.log("success");
             },
             error: function (model, response) {
                 //                 console.log(response);
                 var errorMsg = JSON.parse(response.responseText);
                 $(".errorMessage").html('<div class="alert alert-error">' + errorMsg.Error + '</div>');
             }
         });
        },
        productTabs: function (e) {
            e.preventDefault();
            $(this).tab('show');
        },
        productDetails: function (e) {
            e.preventDefault();
            $("#productName").val($(e.currentTarget).html());
            var ID = $(e.currentTarget).data("id");
            var item = this.collection.get(ID);
            console.log("start..........");
            console.log(item);
            console.log(ID)
            //            console.log(this.collection);
            console.log(this.collection.models.get(item));
            console.log("end..........");
            $('.modal').modal('toggle');
        }
    });
    return new productListView;
});

UPDATE responses

this.collection

b.hasOwnProperty.e
_byCid: Object
_byId: Object
_onModelEvent: function () { [native code] }
_removeReference: function () { [native code] }
length: 2
models: Array[2]
0: b.hasOwnProperty.e
1: b.hasOwnProperty.e
length: 2
__proto__: Array[0]
__proto__: s

It has 2 models and my list also has 2 products

this.model

_callbacks: Object
_changed: false
_changing: false
_escapedAttributes: Object
_previousAttributes: Object
attributes: Object
ID: ""
Name: ""
hRef: ""
__proto__: Object
cid: "c2"
__proto__: s

The attributes are empty

this gives me following

cid: "view1"
collection: b.hasOwnProperty.e
_byCid: Object
_byId: Object
_onModelEvent: function () { [native code] }
_removeReference: function () { [native code] }
length: 2
models: Array[2]
__proto__: s
model: b.hasOwnProperty.e
_callbacks: Object
_changed: false
_changing: false
_escapedAttributes: Object
_previousAttributes: Object
attributes: Object
cid: "c2"
__proto__: s
options: Object
__proto__: s

UPDATE This is what i see when i expand my collections

b.hasOwnProperty.e
_byCid: Object
_byId: Object
_onModelEvent: function () { [native code] }
_removeReference: function () { [native code] }
length: 2
models: Array[2]
0: b.hasOwnProperty.e
_callbacks: Object
_changed: false
_changing: false
_escapedAttributes: Object
_previousAttributes: Object
attributes: Object
ID: "7e0c94fc-7c16-45c9-84a9-a0690103b946"
Name: "dsa"
hRef: "Product/dsa"
__proto__: Object
cid: "c3"
collection: b.hasOwnProperty.e
__proto__: s
1: b.hasOwnProperty.e
length: 2
__proto__: Array[0]
__proto__: s

回答1:

The problem is that you have to bind all function that will call by DOM event, to the instance of your view:

So add this line into your initialize method:

_.bindAll(this, "saveProduct", "productTabs", "productDetails")

Otherwise this in the function will be global window object instead of the instance of your view.

回答2:

Collection.findWhere({_id: ID}) // get the right answer

we could conclude that :

to Model, the key is idAttribute
to Collection, the key is modelId

For example :

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

var Persons = new Col([{
    _id: 1,
    name: 'Ken'
}, {
    _id: 2,
    name: 'Mike'
}, {
    _id: 3,
    name: 'John'
}]);

console.log( Persons.get(1) ); // undefined

If indicate the idAttribute of M :

var M = Backbone.Model.extend({ idAttribute: '_id' });
...
console.log( Persons.get(1) ); // the model of Ken

On some occasions we don't need Model, such as :

var Col = Backbone.Collection.extend();

var Persons = new Col([{
    _id: 1,
    name: 'Ken'
}, {
    _id: 2,
    name: 'Mike'
}, {
    _id: 3,
    name: 'John'
}]);

console.log( Persons.get(2) ); // undefined

For Solving this, we just need to rewrite the original modelId method :

var Col = Backbone.Collection.extend({
    modelId: function() {
        return '_id';
    }
});
...
console.log( Persons.get(2) ); // the model of Mike

P.S : More detail in official docs.

P.S again: Old versions of BackboneJS do not support modelId