# Nestive, A Nested Inheritable Layouts Plugin for Rails
**Note: This is ridiculously alpha proof-of-concept seeking feedback. Things will change.**
Nestive adds powerful layout and view helpers to your Rails app. It's similar to the nested layout technique [already documented in the Rails guides](http://guides.rubyonrails.org/layouts_and_rendering.html#using-nested-layouts) and found in many other nested layout plugins (a technique using `content_for` and rendering the parent layout at the end of the child layout). There's a bunch of problems with this technique, including:
* you can only *append* content to the content buffer with `content_for` (you can't prepend to content, you can't replace it)
* when combined with this nested layout technique, `content_for` actually *prepends* new content to the buffer, because each parent layout is rendered *after* it's child
Nestive is *better* because it addresses these problems.
## Just five methods (so far) – `area`, `extend`, `append`, `prepend`, `replace`.
### Declaring an area of content in your parent layout with `area`:
The `area` helper is a lot like Rails' own `<%= yield :foo %>`, and is used in layouts to define and render a chunk of content in your layout:
<%= area :sidebar %>
Unlike `yield`, `area` will allow your parent layouts to add content to the area at the same time using either a String or a block:
<%= area :sidebar, "Some Content Here" %>
<%= area :sidebar do %>
Some Content Here
<% end %>
It's important to note that this isn't *default* content, it *is* the content (unless a child changes it).
### Extending a layout in a child layout (or view):
Any layout (or view) can declare that it wants to inherit from and extend a parent layout, in this case we're extending `app/views/layouts/application.html.erb`:
<%= extends :application do %>
...
<% end %>
You can nest many levels deep:
# app/views/posts/index.html.erb
<%= extends :blog do %>
...
<% end %>
# app/views/layouts/blog.html.erb
<%= extends :public do %>
...
<% end %>
# app/views/layouts/public.html.erb
<%= extends :application do %>
...
<% end %>
### Appending content to an area:
The implementation details are quite different, but the `append` helper works much like Rails' built-in `content_for`. It will work with either a String or block, adding the new content onto the end of any content previously provided by parent layouts:
<%= extends :application do %>
<%= append :sidebar, "More content." %>
<%= append :sidebar do %>
More content.
<% end %>
<% end %>
### Prepending content to an area:
Exactly what you think it is. The reverse of `append` (duh), adding the new content at the start of any content previously provided by parent layouts:
<%= extends :application do %>
<%= prepend :sidebar, "Content." %>
<%= prepend :sidebar do %>
Content.
<% end %>
<% end %>
### Replacing content
You can also replace any content provided by parent layouts:
<%= extends :application do %>
<%= replace :sidebar, "New content." %>
<%= replace :sidebar do %>
New content.
<% end %>
<% end %>
## The token blog example
Set-up a global layout defining some content areas. Note that there is no `<% yield %>` here.
# app/views/layouts/application.html.erb
<%= area :title %> JustinFrench.com
">
">
<%= area :content do %>
Default content goes here.
<% end %>
<%= area :sidebar do %>
About Me
...
<% end %>
Next, we set-up a `blog` layout that extends `application`, replacing, appending & prepending content to the areas we defined earlier.
# app/views/layouts/blog.html.erb
<%= extends :application do %>
<% replace :title, "My Blog – " %>
<% replace :description, "Justin French blogs here on Ruby, Rails, Design, Formtastic, etc" %>
<% prepend :keywords, "blog, weblog, design links, ruby links, formtastic release notes, " %>
<% end %>
Now our blog index view can extend `blog` and fill in the areas with content specific to the index action.
# app/views/posts/index.html.erb
<%= extends :blog do %>
<% replace :content do %>
My Blog
<% render @articles %>
<% end %>
<% append :content do %>
Blog Roll
<% render @links %>
<% end %>
<% end %>
We also need to instruct the `PostsController` not to wrap the view in a layout of it's own (default Rails behavior), which can be done on an individual action:
# app/controllers/posts_controller.rb
class PostsController < ApplicationController
def index
render :layout => nil
end
end
Or for an entire controller:
# app/controllers/posts_controller.rb
class PostsController < ApplicationController
layout nil
end
Or for every controller:
# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
layout nil
end
We'll find a way to make this easier or a bit more obvious in a future version.
## Installation
* add `gem 'nestive', '~> 0.1'` to your gemfile
* run `bundle`
* add `layout nil` to ApplicationController or the specific controllers you want to use Nestive on (see above)
## TODO
* Figure out how to test it
* Actually use it in an app
* You know, everything!
## Compatibility
Only testing it with Rails 3.1 RCs right now, but it should work with Rails 2 & 3. The dependency is set to ~> 3.0 right now, will change to 2.x when someone can test it works.
*Nestive doesn't monkey patch or fiddle with any default behaviors in Rails.* Use it when you want to, don't when you don't.
## You can help with...
* feedback
* reporting issues
* fixing issues with pull requests
* performance testing
## Twitter
* [@nestivegem](http://twitter.com/nestivegem)
* [@justinfrench](http://twitter.com/justinfrench)