From: The Higgs bozo <higgs.bozo@...>
Date: 2010-01-25T02:40:45+09:00
Subject: Re: Writing proper getter in a Ruby way


> I don't have that:

When I said "A few things about define_method blocks," I meant this,

class P
  define_method :m do |*args, &b|
    [args, b]
  end
end

class C < P
  define_method :m do |*args, &b|
    p [args, b]
    p super
  end
end

C.new.m(:a, :b) { |e| e }

Ruby 1.9:
#=> in `block in <class:C>': implicit argument passing of super from 
method defined by define_method() is not supported. Specify all 
arguments explicitly. (RuntimeError)

Ruby 1.8.7:
#=> [[:a, :b], #<Proc:0x000270b0@test/iacc.rb:15>]
#=> [[:a, :b], nil]

> So another way, probably less 'overkill' you made me think is:
> 
> class Test
>  attr_reader :var
>  def initialize(*args)
>    if args.length > 0
>      @var = :value
>    end
>  end
> 
>  alias :get_var :var
>  def var
>    get_var || 3
>  end
> end
> 
> p Test.new.var #=> 3
> p Test.new(:arg1, :arg2).var #=> :value 

I dunno, it looks convoluted. Might as well go back to "old school"
style, or if it becomes redundant you can use the previously mentioned
technique to abstract like this,

  initialized_attr_reader :var, 3

Going further, you can change the '3' into a block evaluated by newly
created instances.

Or maybe Struct is all you need for initializing variables,

Struct.new(:a, :b).new(2, 3)
#=> #<struct #<Class:0x90bdc> a=2, b=3>
Struct.new(:a, :b).new
#=> #<struct #<Class:0x85070> a=nil, b=nil>

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