Core Concepts

Templates, written in the Handlebars language, describe the user interface of your application. In addition to plain HTML, templates can contain expressions, like {{title}} or {{author}}, which take information from a component or controller and put it into HTML. They can also contain helpers, such as {{#if isAdmin}}30 people have viewed your blog today.{{/if}}. Finally, they can contain components such as a template listing blog posts rendering a component for each post.

Components are the primary way user interfaces are organized in Ember. They consist of two parts: a template, and a source file written in JavaScript that defines the component's behavior. For example, a blog application might have a component for displaying a list of blog posts called all-posts, and another component for displaying an individual post called view-post. If users can upvote a post, the view-post component might define a behavior like when the user clicks the upvote button, increase the vote property's value by 1.

Controllers are very much like components, so much so that in future versions of Ember, controllers will be replaced entirely with components. At the moment, components cannot be routed to (see below), but when this changes, it will be recommended to replace all controllers with components.

Models represent persistent state. For example, a blog application would want to save the content of a blog post when a user publishes it, and so the blog post would have a model defining it, perhaps called the Post model. A model typically persists information to a server, although models can be configured to save to anywhere else, such as the browser's Local Storage.

Routes load a controller and a template. They can also load one or more models to provide data to the controller that can then be displayed by the template. For example, an all-posts route might load all the blog posts from the Post model, load the all-posts controller, and render the all-posts template. Similarly, a view-post route might load the model for the blog post to be shown, load the view-post controller, and render the view-post template.

The router maps a URL to a route. For example, when a user visits the /posts URL, the router might load the all-posts route. The router can also load nested routes. For example, if our blogging app had a list of blog posts on the left of the screen and then showed the current blog post on the right, we'd say that the view-post route was nested inside the all-posts route.

Perhaps the most important thing to remember about Ember is that the URL drives the state of the application. The URL determines what route to load, which in turn determines what model, controller, and template to load.