From: Robert Klemme <shortcutter@...>
Date: 2008-11-07T08:03:10+09:00
Subject: Re: Creating object from hash

On 06.11.2008 21:44, Davi Barbosa wrote:
> I'm creating an object from a hash using this:
> 
> class Computer
>   def initialize(hash)
>     hash.each do |k,v|
>       instance_variable_set("@#{k}", v)  ## create and initialize an
> instance variable for this key/value pair
>       instance_eval %Q{ class << self ; attr_reader #{k.intern.inspect}
> ; end }
>     end
>   end
> end
> 
> This works fine except if I need to define a method with the same name
> of a key (if I need an complicated getter/setter for example). So I
> added a test to attr_reader line:
> instance_eval %Q{ class << self ; attr_reader #{k.intern.inspect} ; end
> } if !instance_eval %Q{defined? #{k}}
> 
> As an Object, some methods are defined (like "id"). So "pc =
> Computer.new({'id' > 1})" does not create the reader for @id and "pc.id"
> calls some unwanted method.
> 
> If I just add "attr_reader :id" everything works. Can I do it directly,
> without adding attr_reader (or attr_accessor) every time that I get an
> error?

You can make your life easier with Struct:

irb(main):001:0> Comp = Struct.new :id do
irb(main):002:1* def initialize(h)
irb(main):003:2> members.each {|m| self[m] = h[m] || h[m.to_sym]}
irb(main):004:2> end
irb(main):005:1> end
=> Comp
irb(main):006:0> c = Comp.new(:id=>133)
=> #<struct Comp id=133>
irb(main):007:0> d = Comp.new("id"=>133)
=> #<struct Comp id=133>
irb(main):008:0>

Kind regards

	robert