creating/accessing class vars from modules being used as mixins?

[Christopher J. Bottaro]

Hello,
I'm writing a module that is to be used as a mixin for classes. I
cannot create or access class variables from within module methods.
Please look at this small pastie. It contains the module definitions,
class definitions, and some sample code that demonstrates the errors
I'm receiving.

http://pastie.caboo.se/39581

Thanks for the help,
-- Christopher

 

[James Edward Gray II]

I'm writing a module that is to be used as a mixin for classes. I
cannot create or access class variables from within module methods.
Please look at this small pastie. It contains the module definitions,
class definitions, and some sample code that demonstrates the errors
I'm receiving.

Class variables have confusing inheritance rules, that I don't think
are worth learning. (They are changing in a future version of Ruby.)

Instead, it's almost always easier to use instance variables on the
class/module itself. Your code could do this with changes like:

module MyModule

def self.included base
base.extend ForBase
end # def self.included

module ForBase

def message
@message
end

def message=(message)
@message = message
end

def acts_as_whatever options = {}
include MyModule::InstanceMethods
extend MyModule::ClassMethods

if options.has_key? :message
self.message = options[:message]
else
self.message = "no message"
end
end # def acts_as_whatever

end # module ForBase

module InstanceMethods

def show_message
puts self.class.message
end

end # module InstanceMethods

module ClassMethods

def print_message
puts message
end

end # module ClassMethods

end # module MyModule

James Edward Gray II

 

[Christopher J. Bottaro]

Wow, thanks for the fast response. Your solution worked perfectly.
On a side note, this should definitely be in a FAQ somewhere (if it
isn't already)... it's kind of a hard problem to figure out if you
don't know not to look at class variables.

Thanks again,
-- Christopher

I'm writing a module that is to be used as a mixin for classes. I
cannot create or access class variables from within module methods.
Please look at this small pastie. It contains the module definitions,
class definitions, and some sample code that demonstrates the errors
I'm receiving.

Class variables have confusing inheritance rules, that I don't think
are worth learning. (They are changing in a future version of Ruby.)

Instead, it's almost always easier to use instance variables on the
class/module itself. Your code could do this with changes like:

module MyModule

def self.included base
base.extend ForBase
end # def self.included

module ForBase

def message
@message
end

def message=(message)
@message = message
end

def acts_as_whatever options = {}
include MyModule::InstanceMethods
extend MyModule::ClassMethods

if options.has_key? :message
self.message = options[:message]
else
self.message = "no message"
end
end # def acts_as_whatever

end # module ForBase

module InstanceMethods

def show_message
puts self.class.message
end

end # module InstanceMethods

module ClassMethods

def print_message
puts message
end

end # module ClassMethods

end # module MyModule

James Edward Gray II