We Keep Coding

Issue with getJSON within Backbone view rendering

I'm pretty new to Backbone.js, loving it so far, but I'm having a little trouble trying to get relational data to render.
Within my Backbone view (called ImagesView) I have the following code:
// Render it
render: function () {
var self = this;
// Empty the container first
self.$el.html("")
// Loop through images
self.collection.each(function(img){
// convert `img` to a JSON object
img = img.toJSON()
// Append each one
self.$el.append(self.template(img))
}, self)
}
There are 3 images in the collection, and they are templated correctly with the above code. Within the img object is a user attribute, containing the User ID. I'm trying to return the user's details, and use these within the template instead of the ID. I'm doing that using the code below:
// Render it
render: function () {
var self = this;
// Empty the container first
self.$el.html("")
// Loop through images
self.collection.each(function(img){
// convert `img` to a JSON object
img = img.toJSON()
/* New code START */
// Each img has a `user` attribute containing the userID
// We'll use this to get their details
$.getJSON('/user/' + img.user, {}, function(json, textStatus) {
img.photographer = {
id: json.id,
username: json.username,
real_name: json.real_name
}
/* Moved 1 level deeper */
// Append each one
self.$el.append(self.template(img))
});
/* New code END */
}, self)
}
When I do this, the user's details are returned correctly and inserted into the template, but I now get 3 of each image returned instead of 1 (i.e. 9 in total), in a completely random order. What am I doing wrong? I'm open to using Backbone methods instead of the getJSON if that will make it easier, I just couldn't get it to work myself. I'm using underscore.js for the templating

The random order is likely caused by the requests being fired at very close intervals and responses returning out of the order they were fired in. I'm not sure why you're getting the multiple things, but if your template renders everything and you're calling that 3 times that could be it?
Anyway where I think you're going wrong is putting the responsibility of loading data into the render method. You'd want this to be abstracted so you have a good separation between data concerns and template concerns. As the ordering of the data is of interest, you'll want all 3 requests to have loaded before rendering. There's two different approaches you could take to this depending on if prior to loading this data you have sufficient data to render the view:
If you're waiting on all the data prior to rendering the view then you would want to render a different view (or template of this view) whilst the data is loaded and then replace that with a view showing all the data once it is loaded.
If you have sufficient data to render the view and what you are loading is supplementary, you'd want to render the view with the data you have in render and then once the other data is loaded use a custom method to modify the rendered view to include your data.
If you want to find out when all 3 requests are complete you can use http://api.jquery.com/jquery.when/

How to update the whole Backbone.js collection that in database?

I have a collection (an object list) in database. I can fetch it like: collectionModel.fetch()
But then user changes something on that collection. When user clickes on save button, the whole collection list must be update in database. I thought maybe i can delete() the old one first and then create() it with new one but i could'n achive it. I can't use the update() method because in this case i should find which collection elements has changed but i want to update whole list. How can i do that? Thanks for help.

Do you have a REST api in front of that database? That's how Backbone is made to work with. When your JavaScript code runs model.save(); a PUT request is made to your api for that model.
You question is about saving the whole collection, for that if you want to remain within the default implementation of Backbone you will have to go over all the models in the collection and call save for each of them.
If you want to make one single request to your server you will have to implement a custom method inside your collection. Something like:
MyCollection = Backbone.Collection.extend({
saveAll: function() {
var data = this.toJSON();
return Backbone.$.ajax({
data: { objects: data },
url: '/url/in/your/server/to/update/db'
});
}
});
That's going to send the array of all models in your collection converted to JSON to your server.
Again, you want to have a RESTful API on the server side if you want to make your life with Backbone easy.

If you want to reset collection you have to specify "reset" attribute.
collectionList.fetch({
reset: true,
...
});
But I think it's better to just update it:
collectionList.fetch({
remove: false,
update: true,
merge: true,
...
});

This is a very old question, but I had another approach so I thought I'd post it.
Sometimes my collections have a lot of data and the server doesn't get it all. I solved this by using one of the underscore methods that backbone collections have, invoke (also relies on jquery):
MyCollection = Backbone.Collection.extend({
update: function(callback) {
// Invoke the update method on all models
$.when.apply($, this.invoke('update')).then(() => {
// After complete call the callback method (if passsed)
if(callback) {
callback();
}
});
}
});
You can use it by calling collection.update() when the collection has models in it. A similar method can be used for creating or deleting collections, and this should be modifiable to catch errors but I didn't account for that.

Backbone: Adding a model to a collection from a collection view?

I have some code where I want a NoteCollectionView to add a new Note to the NoteCollection. This is triggered by a function newNote in the NoteCollectionView:
newNote: function(data) {
var note = new Note(data);
this.collection.add(note);
},
I'm still very new to backbone, and I want to make sure this syncs with the server. The concerns I have are:
1) Will simply adding this note to the collection trigger a save() from the server, and update the model with the ID that the server gives it? Or,
2) If the server does not update my model and give me an actual ID, how do I save the model with note.save() and get back an ID from the server?

To address your first question, no, .add will not trigger any kind of call to the server; it will only add a model to a collection.
However, you do have a couple options. One would be to create the new note model, save it to the database, and then add it to the collection:
newNote: function(data) {
var note = new Note(data);
note.save();
this.collection.add(note);
}
The second option is to simply use Backbone's collection.create method. Give it a hash of attributes and it will
Create the model
Save it to the database
Add it to the collection
All in one fell swoop, like so:
newNote: function(data) {
return this.collection.create(data);
}
collection.create also returns the newly created model, illustrated by my return statement above.

Get attributes of model in backbone.js

I have this model
var Item = Backbone.Model.extend({
url: 'http://localhost/InterprisePOS/Product/loaditembycategory/Event Materials'
});
var onSuccess = function(){ alert("success"); };
And a collection
var Items = Backbone.Collection.extend({
model: Item
});
And the rest of my code is here:
var item = new Item();
var items = new Items();
item.fetch({ success: onSuccess });
alert(items.get("ItemCode"));
What I want is to simply get the attributes of the model. Now I have this on firebug. Also when I run it on the browser I get the alert success and the next alert is undefined.
This is the output:
{"ErrorMessage":null,"Items":[{"ErrorMessage":null,"CategoryCode":"Event Materials","ClassCode":null,"Components":null,"GroupCode":null,"ImageURL":null,"ItemCode":"ITEM-123","ItemDescription":"Old World Lamppost\u000d\u000a\u000d\u000a","ItemName":"GET123","ItemType":null,"KitItem":null,"Matrix":null,"Prefix":null,"RetailPrice":107.990000,"SalesTaxCode":null,"UPCCode":null,"UnitMeasureCode":"EACH","UnitsInStock":0,"Value":null,"WholesalePrice":95.000000}]}
NOTE
That is just one of the items it returns. I just posted on item so that it won't be that long.

You are calling get on your collection ( see http://documentcloud.github.com/backbone/#Collection-get)
It seems what you really want is to iterate over the collection, and call get on each item
items.each(function(item) {
item.get('ItemCode');
});
If not, please elaborate!
Additionally, if your model url responds with a list of models, you should be defining the url attribute in your Collection instead of your model.
var Items = Backbone.Collection.extend({
model: Item,
url: 'http://localhost/InterprisePOS/Product/loaditembycategory/Event Materials'
});
And your response should be an array, with Items as array elements [<item1>, <item2>, ...], rather than a JSON object with {'Items': [<item1>, <item2>, ...] }. If you don't want to modify the response, you will have to implement the parse function on your collection ( http://documentcloud.github.com/backbone/#Collection-parse ).
Also, as #chiborg mentions, you are calling get right after fetch (which will complete asynchronously), so there is no guarantee that your data will be available.
The proper solution here is to bind a 'refresh' listener on the collection.
items.on('refresh', function() {
// now you have access to the updated collection
}, items);

This is due to the model loading asynchonously - item.get("ItemCode") will only work after the model has been loaded with fetch. Try calling it in your onSuccess function.
Additionally, note that it won't help to initialize Item directly. What you are trying to do is get an element in the collection Items and then call item.get("ItemCode") on that element, like this:
function onSuccess() {
alert('success')
var item = items.get(13); // get item with id 13
alert(item.get("ItemCode"));
}

backbone.js cache collections and refresh

I have a collection that can potentially contain thousands of models. I have a view that displays a table with 50 rows for each page.
Now I want to be able to cache my data so that when a user loads page 1 of the table and then clicks page 2, the data for page 1 (rows #01-50) will be cached so that when the user clicks page 1 again, backbone won't have to fetch it again.
Also, I want my collection to be able to refresh updated data from the server without performing a RESET, since RESET will delete all the models in a collection, including references of existing model that may exist in my app. Is it possible to fetch data from the server and only update or add new models if necessary by comparing the existing data and the new arriving data?

In my app, I addressed the reset question by adding a new method called fetchNew:
app.Collection = Backbone.Collection.extend({
// fetch list without overwriting existing objects (copied from fetch())
fetchNew: function(options) {
options = options || {};
var collection = this,
success = options.success;
options.success = function(resp, status, xhr) {
_(collection.parse(resp, xhr)).each(function(item) {
// added this conditional block
if (!collection.get(item.id)) {
collection.add(item, {silent:true});
}
});
if (!options.silent) {
collection.trigger('reset', collection, options);
}
if (success) success(collection, resp);
};
return (this.sync || Backbone.sync).call(this, 'read', this, options);
}
});
This is pretty much identical to the standard fetch() method, except for the conditional statement checking for item existence, and using add() by default, rather than reset. Unlike simply passing {add: true} in the options argument, it allows you to retrieve sets of models that may overlap with what you already have loaded - using {add: true} will throw an error if you try to add the same model twice.
This should solve your caching problem, assuming your collection is set up so that you can pass some kind of page parameter in options to tell the server what page of options to send back. You'll probably want to add some sort of data structure within your collection to track which pages you've loaded, to avoid doing unnecessary requests, e.g.:
app.BigCollection = app.Collection.extend({
initialize: function() {
this.loadedPages = {};
},
loadPage: function(pageNumber) {
if (!this.loadedPages[pageNumber]) {
this.fetchNew({
page: pageNumber,
success: function(collection) {
collection.loadedPages[pageNumber] = true;
}
})
}
}
});

Backbone.Collection.fetch has an option {add:true} which will add models into a collection instead of replacing the contents.
myCollection.fetch({add:true})
So, in your first scenario, the items from page2 will get added to the collection.
As far as your 2nd scenario, there's currently no built in way to do that.
According to Jeremy that's something you're supposed to do in your App, and not part of Backbone.
Backbone seems to have a number of issues when being used for collaborative apps where another user might be updating models which you have client side. I get the feeling that Jeremy seems to focus on single-user applications, and the above ticket discussion exemplifies that.
In your case, the simplest way to handle your second scenario is to iterate over your collection and call fetch() on each model. But, that's not very good for performance.
For a better way to do it, I think you're going to have to override collection._add, and go down the line dalyons did on this pull request.

I managed to get update in Backbone 0.9.9 core. Check it out as it's exactly what you need http://backbonejs.org/#Collection-update.