From: Alexandre Mutel <alexandre_mutel@...>
Date: 2009-11-17T06:01:14+09:00
Subject: How to dynamically include a module and update top level?

Hi,
I'm new to Ruby programming, and I'm having some trouble to dynamically
include a module into another module. This question may have been
already posted, I tried to find it without any success, sorry to ask it
probably again (I found Ruby really powerful, but there are some obscure
behavior that i still don't understand!)

So my problem is simple. When trying with "static" include, it's working
as i understand it:

irb(main):001:0> module A
irb(main):002:1>   def test()
irb(main):003:2>     "test"
irb(main):004:2>     end
irb(main):005:1>   end
=> nil
irb(main):006:0> module B
irb(main):007:1>   include A
irb(main):008:1>   end
=> B
irb(main):009:0> include B
=> Object
irb(main):010:0> test
=> "test"

But when I'm trying to load the module A through a module_eval on module
B, this is not working:

module A
    def self.included(mod)
        puts "#{self} included in #{mod}"
    end

    def testA()
        "testA"
    end
end

module B
    class Includer
       def self.include_dyn(name)
           B.module_eval "include #{name}"
       end
    end
end

irb(main):017:0> include B
=> Object
irb(main):018:0> Includer.include_dyn "A"
A included in B
=> B
irb(main):019:0> testA
NameError: undefined local variable or method `testA' for main:Object
  from (irb):19
  from :0

__________________________

The weird thing is the included callback is saying that A is include in
B... so why the testA method is not expanded to the top level?
after this, if i try to include B again, and call testA, it's working...
but i thought that as soon as a module is mixed-in, every method added
later are available to the top-includer...

It's possible to dynamically mixin A into B, and automatically having
the includer of B (the top level in my example), being updated?


Thanks!
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