From: "A. S. Bradbury" <asbradbury@...>
Date: 2006-08-08T20:54:34+09:00
Subject: Re: method_missing to define_method

On Monday 07 August 2006 04:07, Matt Todd wrote:
> Given the circumstance that you don't want to explicitly predefine
> your methods for properties, etc, but that you're certain your
> parameters won't somehow change to affect your design, would it be
> beneficial to have method_missing define the method so that
> method_missing doesn't have to be called in case the property special
> method is called again?
>
> For instance...
>
> class Person
>   @attributes = {}
>   def initialize attributes
>     @attributes.merge! attributes
>   end
>   def method_missing name
>     if @attributes.has_key? name
>       class_eval do
>         define_method(name) do |name|
>           @attributes[name]
>         end
>       end
>     else
>       # other magic
>     end
>   end
> end
>
> So, if I do...
>
> p = Person.new { :name => "Papa", :age => 66, :phone => "404-932-3955" }
>
> the first time I ask for...
>
> p.age
>
> the method :age is created. And the next time I call it, then it just
> executes the method I juist created.

Have you seen OpenStruct in the standard library?

require 'ostruct'
p = OpenStruct.new({ :name => "Papa", :age => 66, :phone => "404-932-3955" })

You can add new fields after object creation, p.occupation="Doctor". 

I'm also curious as to whether there's any advantage to defining methods (as 
OpenStruct does) vs just looking up hash keys in method_missing.

Alex