If you are writing you own mix-in modules in Rails3 and haven’t taken a look at ActiveSupport::Concern yet, I recommend checking out this blog posting for an outline of why you should be using it:
http://www.strictlyuntyped.com/2010/05/tweaking-on-rails-30-2.html
If you are already using this then good for you and you can continue on.
Here’s a little “stumbling block” with ActiveSupport::Concern that I found the other day that I wanted to share with people. If you have the following code:
module Bar
extend ActiveSupport::Concern
included do
attr_accessor :baz
end
def baz
"Baz"
end
end
class Foo
include Bar
end
puts Foo.new.baz
You might expect the puts to write out “Baz” but it writes out nil instead. Why is that? It has to do with the order in which ActiveSupport::Concern tacks all of the module code into the class including the module. If you
change “attr_accessor” to attr_writer” all works as planned.
So yes you might be saying “why do you have attr_accessor when you define a getter method for baz?” and my response is “because it worked ok before I factored the code out into a module for reuse”.
About the Author
