Backbone views can't access jQuery selectors

Question

I have a Backbone View which handles a registration component, because this required a lot of form access I had the idea to store the form selectors in an object property.

define(["models/security/user", 'text!templates/security/registration.html'], function(SecurityUserModel, Template){

    var SecurityRegistrationView;

    SecurityRegistrationView = Backbone.View.extend({
        initialize: function(){
            this.model = new SecurityUserModel();
            this.model.bind("validated:valid", this.valid);
            this.model.bind("validated:invalid", this.invalid);

            Backbone.Validation.bind(this);

            this.render();
        },
        render: function(){
            $(this.el).append(Template);
        },
        events: {
            "submit form": "submit"
        },
        form: {
            "username": $("#_user_username")
            , "email": $("#_user_email")
            , "password": $("#_user_password")
        },
        submit: function(e){
            e.preventDefault();

            this.model.set("username", this.form.username.val());
            this.model.set("password", this.form.email.val());
            this.model.set("email", this.form.password.val());
            this.model.validate();


            // debug    
            console.log([this.form, this.form.username.val(), this.form.email.val()]);

            if (this.model.isValid) {
                this.model.save();
            }
        },
        valid: function(model, attrs){
            // error
            this.form.attrs[0].username.parent("div.control-group").addClass("success");
        },
        invalid: function(model, attrs){
            // error
            this.form.attrs[0].username.parent("div.control-group").addClass("error");
        }
    });

    return SecurityRegistrationView;
});

When I console.log this.form, I get an object which looks quite good nothing undefined or weird:

[
Object
    email: e.fn.e.init[0]
        context: HTMLDocument
        selector: "#_user_email"
        __proto__: Object[0]
    password: e.fn.e.init[0]
        context: HTMLDocument
        selector: "#_user_password"
        __proto__: Object[0]
    username: e.fn.e.init[0]
        context: HTMLDocument
        selector: "#_user_username"
        __proto__: Object[0]
    __proto__: Object
]

Loggin an jquery function accessing the selectors (this.form.username.val()) fails with undefined.

Why can't use jQuery functions on properties ($el uses this to) where is the thinking error?

Answer 1

I think the problem is, form: {...} is evaluated before render is called -- and the HTML elements you query are created in render .

Maybe you can try to do this at the end inside the render function :

this.form = {
            "username": $("#_user_username")
            , "email": $("#_user_email")
            , "password": $("#_user_password")
        }

Answer 2

You are not using the selector in the right way. You need to scope your jQuery to your view doing this:

invalidateForm: {
  "username": this.$("#_user_username"), 
  "email": this.$("#_user_email"),
  "password": this.$("#_user_password")
},

And render must be in this way:

render: function(){
  this.$el.append(Template);
  this.invalidateForm();
},

Also use this.$el instead of $(this.el) to have more efficient performance, it is a cached version of the view element.

Answer 3

it's a context problem,you can update you code like this:

initialize: function(){
    _.bindAll(this, 'render', 'submit', 'valid','invalid');
    this.model = new SecurityUserModel();
    .....
}

about _.bindAll ,you can see this: Does backbone do _.bindAll by default now? https://stackoverflow.com/a/6396224/1303663

EDIT:>>>>>>>>>>>>

Sorry, I did not fully understand what you mean. you can try this,I think this is what you want:

render: function(){
        $(this.el).append(Template);
        this.initform();
    },
.....
initform: function(){            
        this.form = {};
        this.form.username = $("#_user_username");
        this.form.email = $("#_user_email");
        this.form.password = $("#_user_password");
    },

No other changes