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fix formatting in engines guide; also removed a couple of non-existen…

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1 parent fff3e75 commit 0b67751d62116a314d3d9c631d26d22dc0331067 @vijaydev vijaydev committed Apr 2, 2012
Showing with 25 additions and 35 deletions.
  1. +25 −35 guides/source/engines.textile
@@ -16,7 +16,7 @@ Engines can be considered miniature applications that provide functionality to t
Therefore, engines and applications can be thought of almost the same thing, just with very minor differences, as you'll see throughout this guide. Engines and applications also share a common structure.
-Engines are also closely related to plugins where the two share a common +lib+ directory structure and are both generated using the +rails plugin new+ generator. The difference being that an engine is considered a "full plugin" by Rails -- as indicated by the +--full+ option that's passed to the generator command -- but this guide will refer to them simply as "engines" throughout. An engine *can* be a plugin, and a plugin *can* be an engine.
+Engines are also closely related to plugins where the two share a common +lib+ directory structure and are both generated using the +rails plugin new+ generator. The difference being that an engine is considered a "full plugin" by Rails as indicated by the +--full+ option that's passed to the generator command, but this guide will refer to them simply as "engines" throughout. An engine *can* be a plugin, and a plugin *can* be an engine.
The engine that will be created in this guide will be called "blorgh". The engine will provide blogging functionality to its host applications, allowing for new posts and comments to be created. At the beginning of this guide, you will be working solely within the engine itself, but in later sections you'll see how to hook it into an application.
@@ -51,7 +51,7 @@ h5. Critical files
At the root of this brand new engine's directory, lives a +blorgh.gemspec+ file. When you include the engine into the application later on, you will do so with this line in a Rails application's +Gemfile+:
<ruby>
- gem 'blorgh', :path => "vendor/engines/blorgh"
+gem 'blorgh', :path => "vendor/engines/blorgh"
</ruby>
By specifying it as a gem within the +Gemfile+, Bundler will load it as such, parsing this +blorgh.gemspec+ file and requiring a file within the +lib+ directory called +lib/blorgh.rb+. This file requires the +blorgh/engine.rb+ file (located at +lib/blorgh/engine.rb+) and defines a base module called +Blorgh+.
@@ -115,7 +115,6 @@ The +test+ directory is where tests for the engine will go. To test the engine,
<ruby>
Rails.application.routes.draw do
-
mount Blorgh::Engine => "/blorgh"
end
</ruby>
@@ -179,7 +178,6 @@ After that, a line for the resource is inserted into the +config/routes.rb+ file
<ruby>
Blorgh::Engine.routes.draw do
resources :posts
-
end
</ruby>
@@ -219,17 +217,13 @@ By default, the scaffold styling is not applied to the engine as the engine's la
<%= stylesheet_link_tag "scaffold" %>
</erb>
-You can see what the engine has so far by running +rake db:migrate+ at the root of our engine to run the migration generated by the scaffold generator, and then running +rails server+ in +test/dummy+. When you open +http://localhost:3000/blorgh/posts+ you will see the default scaffold that has been generated.
-
-!images/engines_scaffold.png(Blank engine scaffold)!
-
-Click around! You've just generated your first engine's first functions.
+You can see what the engine has so far by running +rake db:migrate+ at the root of our engine to run the migration generated by the scaffold generator, and then running +rails server+ in +test/dummy+. When you open +http://localhost:3000/blorgh/posts+ you will see the default scaffold that has been generated. Click around! You've just generated your first engine's first functions.
If you'd rather play around in the console, +rails console+ will also work just like a Rails application. Remember: the +Post+ model is namespaced, so to reference it you must call it as +Blorgh::Post+.
<ruby>
- >> Blorgh::Post.find(1)
- => #<Blorgh::Post id: 1 ...>
+>> Blorgh::Post.find(1)
+=> #<Blorgh::Post id: 1 ...>
</ruby>
One final thing is that the +posts+ resource for this engine should be the root of the engine. Whenever someone goes to the root path where the engine is mounted, they should be shown a list of posts. This can be made to happen if this line is inserted into the +config/routes.rb+ file inside the engine:
@@ -355,11 +349,11 @@ end
This is the final part required to get the new comment form working. Displaying the comments however, is not quite right yet. If you were to create a comment right now you would see this error:
-<text>
- Missing partial blorgh/comments/comment with {:handlers=>[:erb, :builder], :formats=>[:html], :locale=>[:en, :en]}. Searched in:
- * "/Users/ryan/Sites/side_projects/blorgh/test/dummy/app/views"
- * "/Users/ryan/Sites/side_projects/blorgh/app/views"
-</text>
+<plain>
+Missing partial blorgh/comments/comment with {:handlers=>[:erb, :builder], :formats=>[:html], :locale=>[:en, :en]}. Searched in:
+ * "/Users/ryan/Sites/side_projects/blorgh/test/dummy/app/views"
+ * "/Users/ryan/Sites/side_projects/blorgh/app/views"
+</plain>
The engine is unable to find the partial required for rendering the comments. Rails has looked firstly in the application's (+test/dummy+) +app/views+ directory and then in the engine's +app/views+ directory. When it can't find it, it will throw this error. The engine knows to look for +blorgh/comments/comment+ because the model object it is receiving is from the +Blorgh::Comment+ class.
@@ -511,11 +505,11 @@ $ rake blorgh:install:migrations
Notice here that only _one_ migration was copied over here. This is because the first two migrations were copied over the first time this command was run.
-<shell>
- NOTE: Migration [timestamp]_create_blorgh_posts.rb from blorgh has been skipped. Migration with the same name already exists.
- NOTE: Migration [timestamp]_create_blorgh_comments.rb from blorgh has been skipped. Migration with the same name already exists.
- Copied migration [timestamp]_add_author_id_to_blorgh_posts.rb from blorgh
-</shell>
+<plain>
+NOTE Migration [timestamp]_create_blorgh_posts.rb from blorgh has been skipped. Migration with the same name already exists.
+NOTE Migration [timestamp]_create_blorgh_comments.rb from blorgh has been skipped. Migration with the same name already exists.
+Copied migration [timestamp]_add_author_id_to_blorgh_posts.rb from blorgh
+</plain>
Run this migration using this command:
@@ -536,9 +530,9 @@ Finally, the author's name should be displayed on the post's page. Add this code
By outputting +@post.author+ using the +<%=+ tag the +to_s+ method will be called on the object. By default, this will look quite ugly:
-<text>
+<plain>
#<User:0x00000100ccb3b0>
-</text>
+</plain>
This is undesirable and it would be much better to have the user's name there. To do this, add a +to_s+ method to the +User+ class within the application:
@@ -581,9 +575,9 @@ self.author = Blorgh.user_class.constantize.find_or_create_by_name(author_name)
To save having to call +constantize+ on the +user_class+ result all the time, you could instead just override the +user_class+ getter method inside the +Blorgh+ module in the +lib/blorgh.rb+ file to always call +constantize+ on the saved value before returning the result:
<ruby>
- def self.user_class
- @@user_class.constantize
- end
+def self.user_class
+ @@user_class.constantize
+end
</ruby>
This would then turn the above code for +self.author=+ into this:
@@ -663,20 +657,16 @@ Try this now by creating a new file at +app/views/blorgh/posts/index.html.erb+ a
<% end %>
</erb>
-Rather than looking like the default scaffold, the page will now look like this:
-
-!images/engines_post_override.png(Engine scaffold overridden)!
-
h4. Routes
Routes inside an engine are, by default, isolated from the application. This is done by the +isolate_namespace+ call inside the +Engine+ class. This essentially means that the application and its engines can have identically named routes, and that they will not clash.
Routes inside an engine are drawn on the +Engine+ class within +config/routes.rb+, like this:
<ruby>
- Blorgh::Engine.routes.draw do
- resources :posts
- end
+Blorgh::Engine.routes.draw do
+ resources :posts
+end
</ruby>
By having isolated routes such as this, if you wish to link to an area of an engine from within an application, you will need to use the engine's routing proxy method. Calls to normal routing methods such as +posts_path+ may end up going to undesired locations if both the application and the engine both have such a helper defined.
@@ -717,11 +707,11 @@ Imagine that you did have an asset located at +app/assets/stylesheets/blorgh/sty
You can also specify these assets as dependencies of other assets using the Asset Pipeline require statements in processed files:
-<css>
+<plain>
/*
*= require blorgh/style
*/
-</css>
+</plain>
h4. Separate Assets & Precompiling

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