From: Bryan JJ Buckley <jj@...>
Date: 2008-05-30T01:06:53+09:00
Subject: Re: Constants in modules

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Two things - firstly, Ruby is interpreted, so invert_hash needs to be 
declared *before* you use it. Then, your methods need to be module 
methods - just put a "self." before each one, and it should work.

Luis Crespo wrote:
> Hello,
>
> I need to do something like this (this is a simplified version of some
> other code, of course, but I don't want to get you lost in details
> unrelated to the problem):
>
> module M
>
>   CONST_A = { 'k1' => 'v1', 'k2' => 'v2' }
>   CONST_B = invert_hash(CONST_A)
>
>   def method1
>     # Do something with CONST_A
>     puts CONST_A
>   end
>
>   def method2
>     # Do something with CONST_B
>     puts CONST_B
>   end
>
>   def invert_hash(h)
>     inverted = {}
>     h.each_pair { |k, v| inverted[v] = k }
>     inverted
>   end
>
> end
>
> My intention is to be able to calculate CONST_B by invoking a method in
> the module itself... but I get this error message:
>
> tests.rb:4: undefined method `invert_hash' for M:Module (NoMethodError)
>   from tests.rb:1
>
> I have tried lots of combinations by prefixing the module name, using
> ::, using module_function, etc., but nothing has worked.
>
> Is there a way to do this? Of course I know there are obvious
> workarounds such as defining the method outside the module, but that
> would be quite ugly... and there should be a way to use code in my own
> module from my own module!!!
>
> Thanks in advance for your help,
>
>     Luis.
>   

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