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Best method for rendering collection in Backbone

I'm using Backbone and I have the following model and collection
App.Models.Person = Backbone.Model.extend({
});
App.Collections.People = Backbone.Collection.extend({
model: App.Models.Person,
url: 'api/people',
});
However what I'm struggling on is the best way to render this collection. Here's how I've done it so far which works but doesn't seem to be the most elegant solution
App.Views.PeopleView = Backbone.View.extend({
el: $(".people"),
initialize: function () {
this.collection = new App.Collections.People();
//This seems like a bad way to do it?
var that = this;
this.collection.fetch({success: function(){
that.render();
}});
},
render: function () {
var that = this;
_.each(this.collection.models, function (item) {
that.renderPerson(item);
}, this);
},
I'm fairly new to Backbone but have to assign this to a different variable to I use it inside of the success function just seems like a bad way of doing things? Any help on best practices would be appreciated.

Backbone allows you to register for events that you can react to. When the collection is synchronized with the server, it will always fire the sync event. You can choose to listen for that event and call any given method. For instance ...
initialize: function () {
this.collection = new App.Collections.People();
this.listenTo(this.collection, "sync", this.render);
// Fetch the initial state of the collection
this.collection.fetch();
}
... will set up your collection so that it would always call this.render() whenever sync occurs.
The docs on Backbone Events are succinct but pretty good. Keep in mind a few things:
The method you use to register event listeners (i.e. listenTo or on) changes how you provide the context of the called function. listenTo, for instance, will use the current context automatically; on will not. This piece of the docs explains it pretty well.
If you need to remove a view, you will need to disconnect event listeners. The easiest way to do that is to use listenTo to connect them in the first place; then when destroying the view you can just call view.stopListening().
For rendering, there are a lots of suggestions for how to do it. Generally having a view to render each individual model is one way. You can also use Backbone.Collection#each to iterate over the models and control the scope of the iterating function. For instance:
render: function() {
this.collection.each(function(model) {
var view = new App.Collections.PersonView({ model: model });
view.render();
this.$el.append(view.$el);
}, this);
}
Note the second argument to .each specifies the scope of the iterator. (Again, have a look at the docs on controlling scope. If you'd rather have a framework help out with the rendering, check out Marionette's CollectionView and ItemView.

If your view is supposed to just render the collection you can send the collection to temnplate and iterate through in template, otherwise you can create another subView for that purpose or send the individual models of the collection to another subview and append to the container, hope it was helpful.

How to modelEvents work in Marionette.CompositeView

I started to learn Marionette.View concept.for this I created model with 1 attribute and assign default value.
I have dropdown list in my html file. Whenever it changes it triggers a function name as myfunction.Inside myFunction I changed model attribute value.
Whenever attribute value changes automatically it triggers another function.that event I written inside Marionette.CompositeView.but it's not working.
Earlier I did same thing using myModel.on there it's working fine.But it's not working modelEvents in Marionette.CompositeView.
let's check the following code.
var mymodel=Backbone.Model.extend({
defaults:{
"name":"oldValue"
}
});
var mymodelObj=new mymodel();
//marionette.View code
var backView=Backbone.Marionette.CompositeView.extend({
events:{
"change #pop1":"myFunction"
},
myFunction:function(){
mymodelObj.set({name:"updatedValue"})
},
modelEvents:{
"change:name":"myFunction1"
},
myFunction1:function(){
alert("Hi");
}
});
//creating instance
var backViewObj=new backView({el:$("#sidebar")});
How can I fix this.
Right Now I am trying to understanding where Marionette.js useful in my Backbone Applications.

If I am not mistaken, model is not attached to the view you have created. For modelEvents to be triggered, there should be a model attribute in CompositeView. For this you should specify the model during initialization of CompositeView;
var backViewObj=new backView({el:$("#sidebar"), model : mymodelObj});

To do this though you need to pass the model in when creating the backView like so:
var backViewObj = new backView({ el:$("#sidebar"), model: myModel });
Marionette accomplishes this by overriding delegateEvents which Backbone.View calls in it's constructor and delegating your modelEvents object to the model:
Marionette.bindEntityEvents(this, this.model, Marionette.getOption(this, "modelEvents"));
Based on your comments above I think that you're unclear about the different types of views that Backbone.Marionette provides as you are asking how to pass more model instances. I also was unclear when I began using Marionette.
Marionette.ItemView represents a single model.
Marionette.CollectionView represents a collection and renders a Marionette.ItemView for every model in the collection. It does not have the ability to render a template.
Marionette.CompositeView represents both a model and a collection (leaf and branch in a tree structure). This is for recursive data structures although you can use a CompositeView to render a template (like a table header, etc.) and use itemViewContainer to place the itemViews in a specific element.
If you want your CompositeView to be able to render multiple models you'll need to pass a collection of models into the CompositeView and not one single model:

Backbone JS: can one view trigger updates in other views?

In my simple project I have 2 views - a line item view (Brand) and App. I have attached function that allows selecting multiple items:
var BrandView = Backbone.View.extend({
...some code...
toggle_select: function() {
this.model.selected = !this.model.selected;
if(this.model.selected) $(this.el).addClass('selected');
else $(this.el).removeClass('selected');
return this;
}
});
var AppView = Backbone.View.extend({
...some code...
delete_selected: function() {
_.each(Brands.selected(), function(model){
model.delete_selected();
});
return false;
},
});
Thing is, I want to know how many items are selected. In this setup selecting is NOT affecting the model and thus not firing any events. And from MVC concept I understand that views should not be directly talking to other views. So how can AppView know that something is being selected in BrandViews?
And more specifically, I AppView to know how many items were selected, so if more than 1 is selected, I show a menu for multiple selection.

You might want to have a read of this discussion of Backbone pub/sub events:
http://lostechies.com/derickbailey/2011/07/19/references-routing-and-the-event-aggregator-coordinating-views-in-backbone-js/
I like to add it in as a global event mechanism:
Backbone.pubSub = _.extend({}, Backbone.Events);
Then in one view you can trigger an event:
Backbone.pubSub.trigger('my-event', payload);
And in another you can listen:
Backbone.pubSub.on('my-event', this.onMyEvent, this);

I use what Addy Osmani calls the mediator pattern http://addyosmani.com/largescalejavascript/#mediatorpattern. The whole article is well worth a read.
Basically it is an event manager that allows you to subscribe to and publish events. So your AppView would subscript to an event, i.e. 'selected'. Then the BrandView would publish the 'selected' event.
The reason I like this is it allows you to send events between views, without the views being directly bound together.
For Example
var mediator = new Mediator(); //LOOK AT THE LINK FOR IMPLEMENTATION
var BrandView = Backbone.View.extend({
toggle_select: function() {
...
mediator.publish('selected', any, data, you, want);
return this;
}
});
var AppView = Backbone.View.extend({
initialize: function() {
mediator.subscribe('selected', this.delete_selected)
},
delete_selected: function(any, data, you, want) {
... do something ...
},
});
This way your app view doesn't care if it is a BrandView or FooView that publishes the 'selected' event, only that the event occured. As a result, I find it a maintainable way to manage events between parts of you application, not just views.
If you read further about the 'Facade', you can create a nice permissions structure. This would allow you to say only an 'AppView' can subscribe to my 'selected' event. I find this helpful as it makes it very clear where the events are being used.

Ignoring the problems with this that you already mention in your post, you can bind and trigger events to/from the global Backbone.Event object, which will allow anything to talk to anything else. Definitely not the best solution, and if you have views chatting with one another then you should consider refactoring that. But there ya go! Hope this helps.

Here is my case with a similar need: Backbone listenTo seemed like a solution to redirect to login page for timed out or not authenticated requests.
I added event handler to my router and made it listen to the global event such as:
Backbone.Router.extend({
onNotAuthenticated:function(errMsg){
var redirectView = new LoginView();
redirectView.displayMessage(errMsg);
this.loadView(redirectView);
},
initialize:function(){
this.listenTo(Backbone,'auth:not-authenticated',this.onNotAuthenticated);
},
.....
});
and in my jquery ajax error handler:
$(document).ajaxError(
function(event, jqxhr, settings, thrownError){
.......
if(httpErrorHeaderValue==="some-value"){
Backbone.trigger("auth:not-authenticated",errMsg);
}
});

You can use Backbone object as the event bus.
This approach is somewhat cleaner but still relies on Global Backbone object though
var view1 = Backbone.View.extend({
_onEvent : function(){
Backbone.trigger('customEvent');
}
});
var view2 = Backbone.View.extend({
initialize : function(){
Backbone.on('customEvent', this._onCustomEvent, this);
},
_onCustomEvent : function(){
// react to document edit.
}
});

Use the same model objects. AppView could be initialized with a collection, and BrandView initialized with one model from that collection. When attributes of a branch object change, any other code that has a reference to that model can read it.
So lets so you have some brands that you fetch via a collection:
var brands = new Brands([]);
brands.fetch();
Now you make an AppView, and an array of BrandView's for each model.
var appView = new AppView({brands: brands});
var brandViews = brands.map(function(brand) {
return new BrandView({brand: brand});
});
The appView and the brandViews now both have access to the same model objects, so when you change one:
brands.get(0).selected = true;
Then it changes when accessed by the views that reference it as well.
console.log(appView.brands.get(0).selected); // true
console.log(brandViews[0].brand.selected) // true

Same as John has suggested above, the Mediator Pattern works really good in this scenario, as Addy Osmani summing this issue up again in Backbone fundamentals.
Wound up using the Backbone.Mediator plugin which is simple and great, and makes my AMD View modules working together seamlessly =)

A Backbone.js view that is a simple select list

I've built a Backbone-powered library that allows a user to add/remove items, much like the Todos example.
Every time an item is add or removed - or the entire collection is refreshed - I need two other select elements that are on other areas of the page to re-populate with the latest items as options. How would this be implemented, do I simply re-populate the select element in the render function of the view which holds a reference to the collection?
I'm tempted to create a view just for the select options but this seems like overkill, especially when considering the view doesn't need to re-act to any events. The select options are used by other views to populate form data.

You're correct: create a unique view for each select option. It's not overkill at all; that's what Views are for. They listen for events from their models, in this case the item list, and redraw themselves upon receiving an event. They have container designations, so once you've established those in the parameters for the View subclass, you never need to think about them again. You can style them independently.
That's the whole point of the Views being the way they are.
More importantly, you could also abstract out "view of a list of things," and then each of your specific views can inherit from that view, and add two features: the filter ("latest"), and the renderer. You have to write the renderer anyway; you may as well exploit a little syntatic sugar to make it clear what you're rendering where. It's better than writing comments.

Not to distract from Elf Sternberg's already excellent answer, but to add a little context:
Don't loop over collections in your templates
If you want to do this, you might as well just use HTML partials and
AJAX. Instead, use a Backbone View that renders its own views (the
granularity is what minimizes server syncs and page refreshes). This
is recursive, you can repeat this pattern until there is no more
associated data to loop over.
— Jonathan Otto in A Conceptual Understanding of Backbone.js For The Everyman
Of course, there are a few gotchas when you want to render subviews.
I did a code search to try and find some examples of how to do this. Turns out that the TodoMVC example is a good model for doing this. From the Strider-CD source (MIT License):
var UserView = Backbone.View.extend({
//... is a class. not sure how to put that here
tagName: "option",
// Cache the template function for a single item.
template: _.template($('#user-item-template').html()),
// The DOM events specific to an item.
// maybe could put links here? but then user couldn't see on mouse-over
// The UserView listens for changes to its model, re-rendering. Since there's
// a one-to-one correspondence between a **User** and a **UserView** in this
// app, we set a direct reference on the model for convenience.
initialize: function() {
_.bindAll(this, 'render');
this.model.bind('change', this.render);
this.model.bind('destroy', this.remove);
},
// Re-render the contents of the User item.
render: function() {
$(this.el).html(this.template(this.model.toJSON()));
return this;
},
// Remove the item, destroy the model.
clear: function() {
this.model.clear();
}
});
// The Application
// ---------------
// Our overall **AppView** is the top-level piece of UI.
var UsersView = Backbone.View.extend({
// Instead of generating a new element, bind to the existing skeleton of
// the App already present in the HTML.
el: $("#user-form"),
// no events here either at this time
// At initialization we kick things off by
// loading list of Users from the db
initialize: function() {
_.bindAll(this, 'addAll', 'addOne','render');
Users.bind('add', this.addOne);
Users.bind('reset', this.addAll);
Users.bind('all', this.render);
console.log("fetching Users");
Users.fetch();
},
// Re-rendering the App just means refreshing the statistics -- the rest
// of the app doesn't change.
render: function() {
console.log("rendering User AppView");
// might want to put some total stats for the Users somewhere on the page
},
// Add a single todo item to the list by creating a view for it, and
// appending its element to the `<ul>`.
addOne: function(User) {
console.log("adding one User: " + User.get("id") + "/" + User.get("email"));
var view = new UserView({model: User});
this.$("#user-list").append(view.render().el);
},
// Add all items in the **Users** collection at once.
addAll: function() {
console.log("adding all Users");
console.log(Users.length + " Users");
Users.each(this.addOne);
}
});
// Finally, we kick things off by creating the **App**.
console.log("starting userapp now");
var UsersApp = new UsersView();
});
Additional examples of a select list view with option sub-views can be found in:
Zipkin source
reviewboard source

backbone.js - collections and views

I understand how to get a collection together, or an individual model. And I can usually get a model's data to display. But I'm not clear at all how to take a collection and get the list of models within that collection to display.
Am I supposed to iterate over the collection and render each model individually?
Is that supposed to be part of the collection's render function?
Or does the collection just have it's own view and somehow I populate the entire collection data into a view?
Just speaking generally, what is the normal method to display a list of models?

From my experience, it's the best to keep in your collection view references to each model's view.
This snippet from the project I'm currently working on should help you get the idea better:
var MyElementsViewClass = Backbone.View.extend({
tagName: 'table',
events: {
// only whole collection events (like table sorting)
// each child view has it's own events
},
initialize: function() {
this._MyElementViews = {}; // view chache for further reuse
_(this).bindAll('add');
this.collection.bind('add', this.add);
},
render: function() {
// some collection rendering related stuff
// like appending <table> or <ul> elements
return this;
},
add: function(m) {
var MyElementView = new MyElementViewClass({
model: m
});
// cache the view
this._MyElementViews[m.get('id')] = MyElementView;
// single model rendering
// like appending <tr> or <li> elements
MyElementView.render();
}
});
Taking this approach allows you to update views more efficiently (re-rendering one row in the table instead of the whole table).

I think there are two ways to do it.
Use a view per item, and manipulate the DOM yourself. This is what the Todos example does. It's a nice way to do things because the event handling for a single model item is clearer. You also can do one template per item. On the downside, you don't have a single template for the collection view as a whole.
Use a view for the whole collection. The main advantage here is that you can do more manipulation in your templates. The downside is that you don't have a template per item, so if you've got a heterogeneous collection, you need to switch in the collection view template code -- bletcherous.
For the second strategy, I've done code that works something like this:
var Goose = Backbone.Model.extend({ });
var Gaggle = Backbone.Collection.extend({
model: Goose;
};
var GaggleView = Backbone.View.extend({
el: $('#gaggle'),
template: _.template($('#gaggle-template').html()),
render: function() {
$(this.el).html(this.template(this.model.toJSON()));
}
};
var g = new Gaggle({id: 69);
g.fetch({success: function(g, response) {
gv = new GaggleView({model: g});
gv.render();
}});
The template code would look something like this:
<script type="text/template" id="gaggle-template">
<ul id="gaggle-list">
<% _.each(gaggle, function(goose) { %>
<li><%- goose.name %></li>
<% }); %>
</ul>
</script>
Note that I use the _ functions (useful!) in the template. I also use the "obj" element, which is captured in the template function. It's probably cheating a bit; passing in {gaggle: [...]} might be nicer, and less dependent on the implementation.
I think when it comes down to it the answer is "There are two ways to do it, and neither one is that great."

The idea of backbone is that view rendering is event driven.
Views attach to Model data change events so that when any data in the model changes the view updates itself for you.
What you're meant to do with collections is manipulate a collection of models at the same time.
I would recommend reading the annotated example.

I've also found this a confusing part of the Backbone framework.
The example Todos code is an example here. It uses 4 classes:
Todo (extends Backbone.Model). This represents a single item to be todone.
TodoList (extends Backbone.Collection). Its "model" property is the Todo class.
TodoView (extends Backbone.View). Its tagName is "li". It uses a template to render a single Todo.
AppView (extends Backbone.View). Its element is the "#todoapp" . Instead of having a "model" property, it uses a global TodoList named "Todos" (it's not clear why...). It binds to the important change events on Todos, and when there's a change, it either adds a single TodoView, or loops through all the Todo instances, adding one TodoView at a time. It doesn't have a single template for rendering; it lets each TodoView render itself, and it has a separate template for rendering the stats area.
It's not really the world's best example for first review. In particular, it doesn't use the Router class to route URLs, nor does it map the model classes to REST resources.
But it seems like the "best practice" might be to keep a view for each member of the collection, and manipulate the DOM elements created by those views directly.