From: Sean O'Halpin <sean.ohalpin@...>
Date: 2009-03-08T13:07:50+09:00
Subject: Re: Can I access or find a object from it's instance variable?

On Sun, Mar 8, 2009 at 2:55 AM, Aki Wakabayashi <zzyzx2001@gmail.com> wrote:
> Hello.
>
> Absolute newb here, and my very first post, so please bear with me...I
> would like to be able to access an object with it's instance variable. I
> simplified my example, but for instance:
>
>
> class Foo
>  attr_accessor :some_id
> end
>
>
> one = Foo.new('7a')
> two = Foo.new('2t')
> three = Foo.new('33')
>
>
> Is it possible to use the instance variable @some_id to access the
> object itself? I was thinking of creating a class method for class Foo
> such as:
>
> class Foo
>  attr_accessor :some_id
>
>  self.find(some_id)
>    # somehow get an array of all the Foo objects, and iterate through
> their
>    # some_id attributes until a match(s) is found, return the object(s)
>  end
> end
>
> ...so I can do something like Foo.find('7a43') to access the object
> 'one'.
>
> I am exhausted from searching how to get an array or hash of objects of
> a given class, and I think I'm going in the wrong direction. Any
> pointers will be greatly appreciated.
>
>
> Thank you in advance :)

Here's one way (not terribly efficient):

class Foo
  attr_accessor :oid
  def initialize(oid)
    @oid = oid
  end

  def self.find(oid)
    found = nil
    ObjectSpace.each_object(self) do |o|
      if o.oid == oid
        found = o
        break
      end
    end
    found
  end
end

one = Foo.new('7a')
two = Foo.new('2t')
three = Foo.new('33')

Foo.find('7a')                # => #<Foo:0x244c8 @oid="7a">

Regards,
Sean