Views vs Components in Ember.js
I am learning ember.js, and I am trying to understand the difference between a view and a component. I see both as a way of making reusable components.
From Ember's website on views:
Views in Ember.js are typically only created for the following reasons:
-When you need sophisticated handling of user events
-When you want to create a re-usable component
From Ember's website on components:
A component is a custom HTML tag whose behavior you implement using JavaScript and whose appearance you describe using Handlebars templates. They allow you to create reusable controls that can simplify your application's templates.
So what is the main difference between a view and a component? And what would be a common example where I would prefer to use a view over a component and vice versa?
Answer
Ember.View
An Ember.View is currently limited to the tags that are created for you by the W3C. But if you wanted to define your own application-specific HTML tags and then implement their behavior using JavaScript? You can't do this actually with a Ember.View.
Ember.Component
That's exactly what components let you do. In fact, it's such a good idea that the W3C is currently working on the Custom Elements spec.
Ember's implementation of components tries to be as closely to the Web Components specification as possible. Once Custom Elements are widely available in browsers, you should be able to easily migrate your Ember components to the W3C standard and have them be usable by other frameworks as well that have adopted the new standard.
This is so important to us that we are working closely with the standards bodies to ensure our implementation of components matches the roadmap of the web platform.
Also important to note is that a Ember.Component is actually a Ember.View (a subclass) but that is completely isolated. Property access in its templates go to the view object and actions are targeted also at the view object. There is no access to the surrounding context or outer controller all contextual information is passed in, which is not the case with a Ember.View which indeed has access to it's surrounding controller, for example inside a view you could do something like this.get('controller') which would give you the controller currently associated with the view.
So what is the main difference between a view and a component?
So, the main difference besides that components let you create your own tags and in some point in the future when Custom Elements are available also migrate/use those components in other frameworks that will support custom elements, is indeed that at some point an ember component will make a view somewhat obsolete depending on the specific implementation case.
And what would be a common example where I would prefer to use a view over a component and vice versa?
Following the above this depends clearly on your use cases. But as a rule of thumb, if you need in your view access to it's surrounding controller etc. use a Ember.View, but if you want to isolated the view and pass in only the information that it needs to work making it context-agnostic and much more reusable, use a Ember.Component.
Hope it helps.
Update
With the publication of Road to Ember 2.0 you are now encouraged to use Components instead of Views in most of the cases.