From: Trans <transfire@...>
Date: 2007-06-16T04:13:08+09:00
Subject: Re: Using extend for initialization settings?



On Jun 15, 1:05 pm, Robert Klemme <shortcut...@googlemail.com> wrote:
> On 15.06.2007 16:44, Trans wrote:
>
>
>
> > It's not uncommon to see initialize method take a hash or a setting
> > proc and apply that to accessors. Eg.
>
> >   def initialize( settings )
> >     settings.each{|k,v| send("{#k}=",v)
> >   end
>
> > or
>
> >   def initialize( &settings )
> >     settings.call(self)
> >   end
>
> > Today I come up with another potential approach:
>
> >   class Hash
> >     def to_module(module_function=false)
> >       m = Module.new
> >       each do |k,v|
> >         m.send(:define_method, k){ v }
> >         m.send(:module_function, k) if module_function
> >       end
> >       return m
> >     end
> >   end
>
> >   M = { :a => 1 }.to_module(true)
> >   p M.a  #=> 1
>
> >   class Foo
> >     def initialize( settings )
> >       extend settings.to_module
> >     end
> >   end
>
> >   f = Foo.new(:x => 9)
> >   p f.x  #=> 9
>
> > Thoughts?
>
> irb(main):001:0> require 'ostruct'
> => true
> irb(main):002:0> f = OpenStruct.new(:x => 9)
> => #<OpenStruct x=9>
> irb(main):003:0> f.x
> => 9

Hmm... I think maybe my point is being missed. The goal is to
initialize a class, not create a simple data struct.

I think the neat thing about this technique is that it could go beyond
just assigning values, and provide a clean means of dependency
injection.

  class Module
    def to_module; self; end
  end

  module Container
    def log(msg)
      puts msg
    end
  end

  class Foo
    def initialize( settings )
      extend settings.to_module
    end
    def report_
      log("Ready.")
    end
  end

  f = Foo.new(Container)

  f.report

produces

  Ready.

T.