Develop Reference

using backbone localStorage on a nested Collection

I'm trying to implement nested Collections exactly like the example I found here: https://stackoverflow.com/a/17453870/295133
The only difference being is that I'm trying to store the data locally using the localStorage plugin.
Here, my Lists would be the Hotels in the example above:
var app = app || {};
(function (){
'use strict';
// List Collection - list of words
//---------------------
var listCollection = Backbone.Collection.extend({
//referebce to this collection's model
model: app.ListModel,
localStorage: new Backbone.LocalStorage('translate-lists')
});
app.listCollection = new listCollection();
})();
(function (){
'use strict';
app.ListModel = Backbone.Model.extend({
initialize: function() {
// because initialize is called after parse
_.defaults(this, {
words: new app.wordCollection
});
},
parse: function(response) {
if (_.has(response, "words")) {
this.words = new app.wordCollection(response.words, {
parse: true
});
delete response.words;
}
return response;
}
});
})();
What the localStorage does is stores the ListModels, but if I add anything to the words collection it soon disappears after I refresh.
Any ideas how I should be saving the entire nested collection?

So got this working and it came down to something in parse but also if you want to ensure you just get the attributes out of your nested collection you should override the toJSON otherwise you get the full collection in what this returns.
Backbone.Model.prototype.toJSON = function() {
var json = _.clone(this.attributes);
for (var attr in json) {
if ((json[attr] instanceof Backbone.Model) || (json[attr] instanceof Backbone.Collection)) {
json[attr] = json[attr].toJSON();
}
}
return json;
};
The main thing that was breaking is in the parse. Is assigns words directly to the model,
this.words = new app.wordCollection(response.words, {
parse: true
});
but this means that it will not show up when toJSON is called as it is not in the attributes (it also means you can't access it via model.get)
so this should be changed to
initialize: function () {
// because initialize is called after parse
_.defaults(this.attributes, {
words: new app.WordCollection()
});
},
parse: function (response) {
if (_.has(response, "words")) {
this.attributes.words = new app.WordCollection(response.words, {
parse: true
});
delete response.words;
}
return response;
}
this way it is added to the attributes of the model on not directly on the model. If you look at this fiddle http://jsfiddle.net/leighking2/t2qcc7my/ and keep hitting run it will create a new model in the collection, save it in local storage then print the results to the console. each time you hit run you should see it grow by 1 (as it gets the previous results local storage) and contain the full information that you want.

Backbone : Make collection from slice of another collection

I'd like to have a paginated view of a collection. I tried using Backbone.Paginator but I just couldn't make it work.
I figured I'd do the pagination myself and I thought it would be a good idea to have my full collection, and then send the view a small collection of the big one, and do this every time someone clicks on 'next'.
I tried doing this but it doesn't work :
var purchaseCollection = new purchaseItemCollection({url:endpoints.purchases});
purchaseCollection.fetch();
var purchaseRangeCollection = new Backbone.Collection(purchaseCollection.models),
purchaseView = new purchaseItemCollectionView({collection:purchaseRangeCollection});
My second collection is only made of one model when it should have severals.
I'm wondering if this is even the best way to do it.
Any advice on how to split a collection into collections, or how to do it in another way would really be appreciated!

You could use a custom object to control a collection representing the list of models currently selected.
For example,
var Slicer = function(opts) {
opts || (opts = {});
// your big collection
this.collection = opts.collection || new Backbone.Collection();
// a collection filled with the currently selected models
this.sliced = new Backbone.Collection();
};
_.extend(Slicer.prototype, Backbone.Events, {
// a method to slice the original collection and fill the container
slice: function(begin, end) {
var models = this.collection.models.slice(begin, end);
this.sliced.reset(models);
// triggers a custom event for convenience
this.trigger('sliced', this.sliced);
}
});
You would then create an instance of this controller and either listen to the custom event sliced on this object or on a reset event on the sliced collection to update your view:
var controller = new Slicer({
collection: purchaseCollection
});
controller.on('sliced', function(c) {
console.log('sliced', c.pluck('id'));
});
controller.sliced.on('reset', function(c) {
console.log('reset', c.pluck('id'));
});
And a demo to play with http://jsfiddle.net/nikoshr/zjgkF/
Note that you also have to take into account the asynchronous nature of fetch, you can't immediately work on the models. In this setup, you would do something like
var purchaseCollection = new purchaseItemCollection(
[], // you have to pass an array
{url:endpoints.purchases} // and then your options
);
purchaseCollection.fetch().then(function() {
// do what you want
// for example
controller.slice(0, 10);
});

You can define the model of your full collection as another independent collection.
Then after fetch(), you will get your collections as the model of your full one.
var PurchaseCollection = Backbone.Collection.extend({
model: Backbone.Collection
})
var purchaseCollection = new PurchaseCollection({url:endpoints.purchases});
purchaseCollection.fetch()
purchaseCollection.each(function (purchaseItem, index) {
//the purchaseItem is what you want...
//do anything...
});
If you want a demo, click here.

Just remember that collection constructor has two attributes (http://backbonejs.org/#Collection-constructor). The first are the models and the second are the options like url etc.

Render a View of Backbone Model returns undefined

Lets say i have a JSON like this:
JSON example, my json is validated on jsonlint and it works.
json_object = {
"texts_model": {
"hello": "hola",
"icon_text": "Icon!"
},
"collection_vias": {
"text": "hola",
"icon_text": "Icon!"
}
};
I have made a Collection that parse the contents of the json and generates model and collections from this json.
App.TemplatesCollection = Backbone.Model.extend({
model: App.TemplateModel,
url: TEMPLATES_SERVICE,
initialize: function(){
this.fetch({
success: (function () {
console.log(' Success ');
}),
error:(function (e) {
//console.log(' Error: ' + e);
}),
complete:(function (e) {
console.log(' Fetch completado con exito. ');
})
});
},
//Here i generate all my models and collections.
parse: function(response){
App.texts = new App.TemplateModel(response.text_model);
App.vias = new App.ViasCollection(response.collection_vias);
return response;
},
//I was trying with the get function but i the only thing i got was undefined.
plain_texts: function(){
return( this.get('plain_texts') ) ;
}
});
And the view is like this:
App.TemplateView = Backbone.View.extend({
el: App.$main_content,
initialize: function(){
_.bindAll(this, 'render');
},
//Here i pass the template(html source) i want to render.
render: function(template){
var html = render(template, this.model.toJSON() );
App.$main_content.html(html);
return this;
}
});
And my start.js where they live all the declarations of my models and views:
//app
App = {
init: function(){
console.log('Iniciando...');
//variables y constantes
App.$main_content = $('#main-content-content');
App.$main_header = $('#main-header-content')
App.$main_navigation = $('#main-navigation-content');
//data
App.templates = new App.TemplatesCollection();
//views
App.templateView = new App.TemplateView({model: App.texts});
//router
App.router = new App.Router();
},
start: function(){
//init
App.init();
//router
Backbone.history.start();
}
}
And the router:
//router
App.Router = Backbone.Router.extend({
routes:{
"" : "index",
":web" : "url"
},
index: function(){
console.log("index");
//Here i do not know what to do, i mean do i have to instiate the View each time i go to index? or only render?
App.templateView = new App.TemplateView({model: App.texts});
App.templateView.render("sections/login/form");
},
url: function(web){
console.log(web);
}
});
//on document ready
$(function(){
App.start();
});
My problem is that when the html is loaded the only thing i have is:
"Uncaught TypeError: Cannot call method 'toJSON' of undefined "
But when i put this on the developer console:
App.templateView = new App.TemplateView({model: App.texts});
App.templateView.render("sections/login/form");
My view is rendered correctly.
Why my view isn't rendered on the load and only when i put my code on the developer console?
How can i render my model on the view on the router url?
Why do i have undefined on the html loaded on the developer console?
----EDIT---
All right,
I think i understand. Maybe I'm generating a problem of a thing that does not have to have a problem.
Now my Model is like this:
App.TemplatesCollection = Backbone.Model.extend({
model: App.TemplateModel,
url: TEMPLATES_SERVICE,
plain_texts: function(){
return this.get('texts') ;
},
initialize: function(){
this.fetch();
}
});
And the View:
App.TemplateView = Backbone.View.extend({
el: App.$main_content,
initialize: function(){
console.log(this.collection);
var ea = this.collection.get('texts');
console.log(ea);
},
render: function(template){
console.log(this.collection);
return this;
}
});
Now i see my collection inside my View.
But when i try to do this to get only the text version on my View:
var ea = this.collection.get('texts');
console.log(ea);
Im getting the error of undefined:
Uncaught TypeError: Cannot call method 'get' of undefined
Any idea about how can i resolve this?
I'm trying to solve this by myself. I do not want to look like im asking to develop my solution.
Thanks in advance.

It's a little hard to read, but at a quick glance: your App.texts = is in in the parse() function of your Collection. As a result, it gets called once the .fetch() on the collection is performed... until then, your App.texts is undefined!
If App.texts is undefined when you create the TemplateView, then the view's model will actually be undefined, and so, in the render, when the template engine you use is doing a toJSON(), it will say that it has an undefined value...
There may be other problems, but this one is the most glaring. Here is a quick&dirty fix: once the fetch() is done, your collection will trigger a reset event. That's your cue for doing the rendering. So, what you can do, is instead of passing the model to the View, you can pass the collection instead:
App.templateView = new App.TemplateView({collection: App.templates});
Now, in your View's initialize, you can do something like:
if(App.texts) {
//Your collection has already fetched and already went through parse()
this.model = App.texts;
this.render("sections/login/form");
} else {
//Your collection hasn't done the fetch yet
view = this;
this.collection.one("reset", function(){
view.model = App.texts;
view.render("sections/login/form");
});
}
If you give a collection as a param to a View's construction, it'll be stored in this.collection, same as with model. The idea here is to use the events to know when to do the rendering, and also let the view tell you when it's ready to render. You could also do something in your render() function to check if the model is defined!
To see if this analysis is correct, you can put a console.log(App.texts); in your index function in the router.
One way to make the code a bit more obvious is to initialize your App.texts and App.vias directly in your App's init. And give a reference to them to your AppTemplatesCollection if you really need to side-load them in the parse of AppTemplates' fetch(). The difference that makes is that you can bind to events from the App.vias collection ('add', 'remove', 'reset') or to the App.texts model ('change').
Another thing I noticed is that you have a collection of App.TemplateModel but you are still creating a App.texts where you put the result of the fetch into your own instance of App.TemplateModel? That doesn't seem right, maybe you have a reason for doing so, but in the most general case, the collection is suppose to handle the creation of the models, especially after a fetch!
The usual use case of the parse() method is to side-load data (other models/collection), change the format (from XML to something JS can understand) or to remove useless keys (for instance user: {id: ..., name: ... }, you'll return response.user so that Backbone can play with the correct hash directly). What you are doing here seems to fall out of this pattern so maybe it's a cause for worry?

In your code you have created collection as :
App.TemplatesCollection = Backbone.Model.extend({
//rest of the code
If you want to create a collection you need to extend Backbone.Collectionand not Backbone.Model.
App.TemplatesCollection = Backbone.Collection.extend({
//rest of the code

Backbone JS: self populate Collection

I have a Backbone collection like this
var ContactsCollection = Backbone.Collection.extend({
model: Contact,
initialize: function () {
//retrieves contacts from web service
//contactsLoaded: is the callback that gets called after
//the contacts get received
loadContacts(this.contactsLoaded);
},
contactsLoaded: function (contacts) {
for (var i = 0; i < contacts.length; i++) {
//TODO populate the collection [models][1]
}
}
});
in other word, I want to self populate the collection's models,
how can I do this ?

Consider using the REST API as Collection#fetch should do exactly what you want.
var ContactsCollection = Backbone.Collection.extend({
model: Contact,
url: '', // set the URL
initialize: function () {
this.fetch();
}});

For a Backbone collection, you needn't to add the model one by one, the framework will do the job. Simply
var ContactsCollection = Backbone.Collection.extend({
model: Contact,
url: '/contacts' // whatever web service url you are using
initialize: function () {
this.fetch();
}
});
If your return from the server is not an JSON array, or it's wrapped with some node, you can override the parse method.
parse: function(response) {
// if it's like {data: [model1, model2, model3...]}
return response.data
}

Assuming you're passing in a list of contact models, do this (you don't need a for loop):
this.add(contacts);
The docs mention you can add models one by one, or as an array.

Agree with #Loamhoof. You should use backbones fetch to accomplish this.
I suggest you move the call to fetch outside the collections initialize method. It would be clearer and more handy to put it with the rest of your applications control flow / router logic. Fetch will return a jqXHR object implements a promise interface. Allowing you to do something like this:
var contactsCollection = new ContactsCollection({});
var p = contactsCollection.fetch();
p.done(function() { ... });
p.error(function() { ... });
p.always(function() { ... });

When do I need a model in backbone.js?

I'm new to Backbone.js, and someone who comes out of the 'standard' model of JS development I'm a little unsure of how to work with the models (or when).
Views seem pretty obvious as it emulates the typical 'listen for event and do something' method that most JS dev's are familiar with.
I built a simple Todo list app and so far haven't seen a need for the model aspect so I'm curious if someone can give me some insight as to how I might apply it to this application, or if it's something that comes into play if I were working with more complex data.
Here's the JS:
Todos = (function(){
var TodoModel = Backbone.Model.extend({
defaults: {
content: null
}
});
var TodoView = Backbone.View.extend({
el: $('#todos'),
newitem: $('#new-item input'),
noitems: $('#no-items'),
initialize: function(){
this.el = $(this.el);
},
events: {
'submit #new-item': 'addItem',
'click .remove-item': 'removeItem'
},
template: $('#item-template').html(),
addItem: function(e) {
e.preventDefault();
this.noitems.remove();
var templ = _.template(this.template);
this.el.append(templ({content: this.newitem.val()}));
this.newitem.val('').focus();
return this;
},
removeItem: function(e){
$(e.target).parent('.item-wrap').remove();
}
});
self = {};
self.start = function(){
new TodoView();
};
return self;
});
$(function(){
new Todos(jQuery).start();
});
Which is running here: http://sandbox.fluidbyte.org/bb-todo

Model and Collection are needed when you have to persist the changes to the server.
Example:
var todo = new TodoModel();
creates a new model. When you have to save the save the changes, call
todo.save();
You can also pass success and error callbacks to save . Save is a wrapper around the ajax function provided by jQuery.
How to use a model in your app.
Add a url field to your model
var TodoModel = Backbone.Model.extend({
defaults: {
content: null
},
url: {
"http://localhost";
}
});
Create model and save it.
addItem: function(e) {
e.preventDefault();
this.noitems.remove();
var templ = _.template(this.template);
this.el.append(templ({content: this.newitem.val()}));
this.newitem.val('').focus();
var todo = new TodoModel({'content':this.newitem.val()});
todo.save();
return this;
},
Make sure your server is running and set the url is set correctly.
Learning Resources:
Check out the annotated source code of Backbone for an excellent
explanation of how things fall into place behind the scenes.
This Quora question has links to many good resources and sample apps.

The model is going to be useful if you ever want to save anything on the server side. Backbone's model is built around a RESTful endpoint. So if for example you set URL root to lists and then store the list information in the model, the model save and fetch methods will let you save/receive JSON describing the mode to/from the server at the lists/<id> endpoint. IE:
ToDoListModel = Backbone.model.extend( {
urlRoot : "lists/" } );
// Once saved, lives at lists/5
list = new ToDoListModel({id: 5, list: ["Take out trash", "Feed Dog"] });
list.save();
So you can use this to interact with data that persists on the server via a RESTful interface. see this tutorial for more.

I disagree with the idea that model is needed only to persist changes (and I am including LocalStorage here, not only the server).
It is nice to have representation of models and collections so that you have object to work with and not only Views. In your example you are only adding and removing divs (html) from the page, which is something you can do normally with jQuery. Having a Model created and added to a Collection everytime you do "add" and maybe removed when you clear it will allow you some nice things, like for example sorting (alphabetically), or filtering (if you want to implement the concept of "complete" to-do).
In your code, for example:
var TodoModel = Backbone.Model.extend({
defaults: {
content: null
complete: false
}
});
var Todos = Backbone.Collection.extend({
model: TodoModel
})
In the View (irrelevant code is skipped):
// snip....
addItem: function(e) {
e.preventDefault();
this.noitems.remove();
var templ = _.template(this.template);
var newTodo = new TodoModel({ content: this.newitem.val() });
this.collection.add(newTodo); // you get the collection property from free from the initializer in Backbone
this.el.append(templ({model: newTodo})); // change the template here of course to use model
this.newitem.val('').focus();
return this;
},
Initialize like this:
self.start = function(){
new TodoView(new Todos());
};
Now you have a backing Collection and you can do all sort of stuff, like filtering. Let's say you have a button for filtering done todos, you hook this handler:
_filterDone: function (ev) {
filtered = this.collection.where({ complete: true });
this.el.html(''); // empty the collection container, I used "el" but you know where you are rendering your todos
_.each(filtered, function (todo) {
this.el.append(templ({model: todo})); // it's as easy as that! :)
});
}
Beware that emptying the container is probably not the best thing if you have events hooked to the inner views but as a starter this works ok.
You may need a hook for setting a todo done. Create a button or checkbox and maybe a function like this:
_setDone: function (ev) {
// you will need to scope properly or "this" here will refer to the element clicked!
todo = this.collection.get($(ev.currentTarget).attr('todo_id')); // if you had the accuracy to put the id of the todo somewhere within the template
todo.set('complete', true);
// some code here to re-render the list
// or remove the todo single view and re-render it
// in the simplest for just redrawr everything
this.el.html('');
_.each(this.collection, function (todo) {
this.el.append(templ({model: todo}));
});
}
The code above would not have been so easy without Models and Collections and as you can see it does not relate in any way with the server.