From: Brian Candler <b.candler@...>
Date: 2011-04-03T16:55:34+09:00
Subject: Re: Using variables in modules

Stefan Salewski wrote in post #990601:
> I have a module named Config with a configuration hash, with
> predefined colors. I access that hash from other modules. That hash
> should have default values, but it should be possible to redefine it.

If you want to do this with a constant then you probably want 
Hash#replace:

Config::Colors = {:red => 1, :blue => 2}
Config::Colors.replace({:red => 3, :blue => 4})

You'll get no warning because the constant still points to the same 
object, you've just mutated that object. But as others have said, a 
class instance variable is probably cleaner.

Hash#merge is useful too when you have defaults, so unspecified keys 
retain their default values:

def configure(settings)
  Config::Colors.replace(Config::Defaults.merge(settings))
end

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