Introduce "Application Concerns" section.

[dgeb]

Replaces the "Services and Initializers" section and expands its
content to include pages explaining Applications and Instances, as
well as Dependency Injection.

All the examples and text have been reviewed and updated for
clarity and compatibility with Ember 2.1.

One caveat is that the Initializers page references the
instance-initializer generator, which is still a WIP at the
moment. I'll try to get that into CLI ASAP.

Closes #827, #789, and #771.

[mixonic]

Exporting a bare function like this is OK? Doesn't this need the Ember.Application.initializer( call?

(applies to several code snippets through this content)

[dgeb]

Sorry, this is only a partial initializer implementation. The part that's left off would be:

export default {
  name: 'logger',
  initialize: initialize
};

I should just add this for clarity.

[dgeb]

... and to all the other initializer examples on this page.

[mixonic]

👏

[dgeb]

Thanks for the review @mixonic. Just pushed a revision.

[michaelrkn]

This looks really awesome! I just have two thoughts about it:

1. The Guides are typically structured from most common/useful features to know about, to more obscure/abstract ideas. The current order makes sense from the perspective of how an application works, but presents the most commonly-used feature (services) last. I'd suggest re-ordering it to:

• Services
• Initializers
• Applications and Instances
• Dependency Injection
• The Container

1. I'd also suggest we move the Run Loop guide into here. Currently it's in Components, which is really not great. It doesn't totally fit in with the rest of the content here, but it's much more closely aligned.

Thanks for the great work!

[dgeb]

I agree that the run loop section would be a better fit here.

I think that we need to lead with the "applications and instances" section because the distinction is a bit confusing without an explanation, and the distinction is referenced throughout the initializers and DI sections.

The container section has been absorbed by the DI section and no longer exists on its own.

[michaelrkn]

Thanks for all your work on this, @dgeb!

[dgeb]

@michaelrkn glad to help!

Let's revisit your ordering / organization concerns with separate PRs. I strongly agree about the run loop section being a better fit here than under components. Also, maybe the sub-section order could be tweaked a bit.

Still waiting to resolve the instance-initializer generator issue over in ember-cli/ember-cli#4218 Hope we can get that merged before the 2.1 guides go live - otherwise, we should make a note in the new instance initializer section.

[michaelrkn]

Sounds good!!