Metaprogramming ActiveRecord Rails

Question

I have the following code in my project`s lib directory

module Pasta  
  module ClassMethods
    def self.has_coordinates
      self.send :include, InstanceMethods     
    end
  end

  module InstanceMethods
    def coordinates
      [longitude ||= 43.0, latitude ||= 25.0]
    end
  end   

  ActiveRecord::Base.extend ClassMethods
end

And it should create a class method for ActiveRecord::Base - has_coordinates - which I can "assign" to models... But I receive the error undefined local variable or method 'has_coordinates'

Thanks in advance!

elektronaut · Accepted Answer · 2010-06-16 22:43:13Z

1

Dropping the self. in ClassMethods should do the trick.

module Pasta  
  module ClassMethods
    def has_coordinates
      self.send :include, InstanceMethods
    end
  end

  module InstanceMethods
    def coordinates
      [longitude ||= 43.0, latitude ||= 25.0]
    end
  end   

  ActiveRecord::Base.extend ClassMethods
end

answered Jun 16, 2010 at 22:43

elektronaut

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2 Comments

Dimitar Vouldjeff Over a year ago

But it does not... :( Even if I make a syntax error in pasta.rb, I do not receive it... Is Rails including the file at all?

elektronaut Over a year ago

Not unless you tell it to. You'll probably have to <code>require 'pasta'</code> somewhere.

John Topley · Accepted Answer · 2010-06-17 08:15:38Z

0

Try this:

module Pasta
  def has_coordinates
    send :include, InstanceMethods
  end

  module InstanceMethods
    def coordinates 
      [longitude ||= 43.0, latitude ||= 25.0] 
    end     
  end
end

ActiveRecord::Base.extend Pasta

Better Ruby Idioms

answered Jun 17, 2010 at 8:15

John Topley

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2 Comments

Dimitar Vouldjeff Over a year ago

Same thing... PS. I am using Rails 2.3.5

Dimitar Vouldjeff Over a year ago

0.o I fixed things up... Thanks!

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