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8. Collections in backbone js – Learning Backbone js

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8. Collections in backbone js – Learning Backbone js

Posted by Mohit Jain on .

This entry is part 8 of 14 in the series for A Complete Guide for Learning Backbone Js


Agenda

So from previous lessons, we know how to create a Person model, We are aware how to create PersonView and us how to define inline and external templates. In this lesson, we will learn collections in backbone js and in the lesson we will learn how to define views for collections in backbone js.

What we have till now

So here is the code that we have from the previous lesson.

var Person = Backbone.Model.extend({
    defaults: {
        name: 'Guest User',
        age: 23,
        occupation: 'worker'
    }
});

var PersonView = Backbone.View.extend({
    tagName: 'li',

    template: _.template( $('#personTemplate').html()),

    initialize: function(){
        this.render();
    },

    render: function(){
        this.$el.html( this.template(this.model.toJSON()));
    }
});

// calls from console

// var person = new Person;  // a person object created...
// var personView = new PersonView({ model: person });
// personView.el   // ---->; You can call this method and it will display the view..
//$(document.body).html(personView.el);  //  --->; This will add output to the dom. This is not ideal but good enough for demo.

Defining a collection

Now from above code if we want to create a new person and add that model in view that it will become messy and it will go so much messy if we have to define some ten people records. Thanks to the backbone that we have collections in backbone js. So here is how we define collections in backbone js.

// A List of People
var PeopleCollection = Backbone.Collection.extend({
    model: Person
});

Setting up the defaults

So we tell collection that what kind of objects we are dealing with by specifying the model attribute. In this case, we have PeopleCollection, so we have Person defined there. So let’s see how to can use it. So we have:

// Person Model
var Person = Backbone.Model.extend({
    defaults: {
        name: 'Guest User',
        age: 30,
        occupation: 'worker'
    }
});

// A List of People
var PeopleCollection = Backbone.Collection.extend({
    model: Person
});

// The View for a Person
var PersonView = Backbone.View.extend({
    tagName: 'li',

    template: _.template( $('#personTemplate').html()),

    initialize: function(){
        this.render();
    },

    render: function(){
        this.$el.html( this.template(this.model.toJSON()));
    }
});

Fire up the console and fire these commands

 var person = new Person;
 var personView = new PersonView({ model: person });
 var peopleCollection = new PeopleCollection();
 peopleCollection.add(person);
 var person2 = new Person({name: "Mohit Jain", age: 25, occupation: "Software Developer"});
 var personView2 = new PersonView({ model: person2 });
 peopleCollection.add(person2);
 peopleCollection
 peopleCollection.toJSON(); // --> returns a list of data attributes

Output on Chrome Console

Lets see what we have on console.

Collections in backbone js

Another way of adding data to collection

Another way to adding data to collections is:

// Person Model
var Person = Backbone.Model.extend({
    defaults: {
        name: 'Guest User',
        age: 30,
        occupation: 'worker'
    }
});

// A List of People
var PeopleCollection = Backbone.Collection.extend({
    model: Person
});

// The View for a Person
var PersonView = Backbone.View.extend({
    tagName: 'li',

    template: _.template( $('#personTemplate').html()),

    initialize: function(){
        this.render();
    },

    render: function(){
        this.$el.html( this.template(this.model.toJSON()));
    }
});

var peopleCollection = new PeopleCollection([
    {
        name: 'Mohit Jain',
        age: 26
    },
    {
        name: 'Taroon Tyagi',
        age: 25,
        occupation: 'web designer'
    },
    {
        name: 'Rahul Narang',
        age: 26,
        occupation: 'Java Developer'
    }
]);

So you can loop over it. Do so many things as collections have so much data stored in it on model objects. It may seem like we can store in the form of the array but collections have their collections view, and that makes them pretty powerful. Let’s talk about collection views in next lesson, and that will help you to understand the importance of collections.


Source code

If you are facing any issues. Check out the source code files at github. I will be creating more and more directories in the same repo regarding each post. Still, if you have any doubts you can comment on the blog post itself, and I will try to reply back asap.

user

Mohit Jain

http://codebeerstartups.com

Rails Developer