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-rw-r--r--railties/guides/source/initialization.textile34
1 files changed, 33 insertions, 1 deletions
diff --git a/railties/guides/source/initialization.textile b/railties/guides/source/initialization.textile
index 738d5cf71a..10937626af 100644
--- a/railties/guides/source/initialization.textile
+++ b/railties/guides/source/initialization.textile
@@ -723,7 +723,39 @@ This file is the first file that sets up configuration with these lines inside t
config.i18n.fallbacks = ActiveSupport::OrderedOptions.new
</ruby>
-The +config+ method here is defined on +Rails::Railtie+ and is defined like this:
+By inheriting from +Rails::Railtie+ the +Rails::Railtie#inherited+ method is called:
+
+<ruby>
+ def inherited(base)
+ unless base.abstract_railtie?
+ base.send(:include, Railtie::Configurable)
+ subclasses << base
+ end
+ end
+</ruby>
+
+This first checks if the Railtie that's inheriting it is a component of Rails itself:
+
+<ruby>
+ABSTRACT_RAILTIES = %w(Rails::Railtie Rails::Plugin Rails::Engine Rails::Application)
+
+...
+
+def abstract_railtie?
+ ABSTRACT_RAILTIES.include?(name)
+end
+</ruby>
+
+Because +I18n::Railtie+ isn't in this list, +abstract_railtie?+ returns +false+. Therefore the +Railtie::Configurable+ module is included into this class and the +subclasses+ method is called and +I18n::Railtie+ is added to this new array.
+
+<ruby>
+def subclasses
+ @subclasses ||= []
+end
+</ruby>
+
+
+The +config+ method used at the top of +I18n::Railtie+ is defined on +Rails::Railtie+ and is defined like this:
<ruby>
def config