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Diffstat (limited to 'guides/source/engines.textile')
| -rw-r--r-- | guides/source/engines.textile | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/guides/source/engines.textile b/guides/source/engines.textile index 36210aedb0..880be57fb5 100644 --- a/guides/source/engines.textile +++ b/guides/source/engines.textile @@ -448,6 +448,8 @@ rake db:migrate SCOPE=blorgh VERSION=0 h4. Using a class provided by the application +h5. Using a model provided by the application + When an engine is created, it may want to use specific classes from an application to provide links between the pieces of the engine and the pieces of the application. In the case of the +blorgh+ engine, making posts and comments have authors would make a lot of sense. Usually, an application would have a +User+ class that would provide the objects that would represent the posts' and comments' authors, but there could be a case where the application calls this class something different, such as +Person+. It's because of this reason that the engine should not hardcode the associations to be exactly for a +User+ class, but should allow for some flexibility around what the class is called. @@ -544,6 +546,19 @@ end Now instead of the ugly Ruby object output the author's name will be displayed. +h5. Using a controller provided by the application + +Because Rails controllers generally share code for things like authentication and accessing session variables, by default they inherit from <tt>ApplicationController</tt>. Rails engines, however are scoped to run independently from the main application, so each engine gets a scoped +ApplicationController+. This namespace prevents code collisions, but often engine controllers should access methods in the main application's +ApplicationController+. An easy way to provide this access is to change the engine's scoped +ApplicationController+ to inherit from the main application's +ApplicationController+. For our Blorgh engine this would be done by changing +app/controllers/blorgh/application_controller.rb+ to look like: + +<ruby> +class Blorgh::ApplicationController < ApplicationController +end +</ruby> + +By default, the engine's controllers inherit from <tt>Blorgh::ApplicationController</tt>. So, after making this change they will have access to the main applications +ApplicationController+ as though they were part of the main application. + +This change does require that the engine is run from a Rails application that has an +ApplicationController+. + h4. Configuring an engine This section covers firstly how you can make the +user_class+ setting of the Blorgh engine configurable, followed by general configuration tips for the engine. @@ -695,7 +710,7 @@ If a template is rendered from within an engine and it's attempting to use one o h4. Assets -Assets within an engine work in an identical way to a full application. Because the engine class inherits from +Rails::Engine+, the application will know to look up in the engine's +app/assets+ directory for potential assets. +Assets within an engine work in an identical way to a full application. Because the engine class inherits from +Rails::Engine+, the application will know to look up in the engine's +app/assets+ and +lib/assets+ directories for potential assets. Much like all the other components of an engine, the assets should also be namespaced. This means if you have an asset called +style.css+, it should be placed at +app/assets/stylesheets/[engine name]/style.css+, rather than +app/assets/stylesheets/style.css+. If this asset wasn't namespaced, then there is a possibility that the host application could have an asset named identically, in which case the application's asset would take precedence and the engine's one would be all but ignored. |