From: Robert Klemme <shortcutter@...>
Date: 2012-05-17T00:13:04+09:00
Subject: Re: Passing attributes to initialize

On Wed, May 16, 2012 at 4:25 PM, Matt Mencel <MR-Mencel@wiu.edu> wrote:
> Hi,
>
> I'm not an OOP person.  Most of the Ruby I write is just scripts and such.  I've found a good place to start using real Class objects though and am having a hard time getting my head around it.
>
> I have this class.  The @members attribute is an array of several 5 digit numbers (could be between 1 and 10 values in the array).  I want to be able to find objects in the Class by using one of the numbers.
>
> class Crosslisting
>  attr_accessor :members, :title, :id
>
>  def initialize(members, name='', id='')
>    @members = members
>    @name = name
>    @id = id
>  end
>
>  def self.find_by_member(member)
>    found = nil
>    ObjectSpace.each_object(Crosslisting) { |o|
>      found = o if o.members.include?(member)
>    }
>    found
>  end
> end
>
> members = ['12345','67890']
> my_obj = Crosslisting.new(members)
> ap Crosslisting.find_by_member('12345')
>
> # OUTPUT USING AWESOME_PRINT GEM
> #<Crosslisting:0x00e77410
>    attr_accessor :id = "",
>    attr_accessor :members = [
>        [0] "12345",
>        [1] "67890"
>    ],
>    attr_accessor :name = ""
>>
>
>
> This seems to work ok.  Am I doing it right or is there a better way?

ObjectSpace is always a crutch.  Better remember all elements
somewhere (e.g. in an instance variable of the class).

class Crosslisting
 attr_accessor :members, :title, :id

 def initialize(members, name='', id='')
   @members = members
   @name = name
   @id = id
   self.class.add(self)
 end

 def self.add(cl)
   (@members ||= []) << cl
 end

 def self.find_by_member(member)
   @members.find {|o| o.members.include?(member)} if @members
 end
end

>  I tried to figure out how to use 'def initialize(*args)' instead of naming all the attributes, but I'm not currently smart enough to make it work apparently.

Why would you want to do that?  The code of #initialize is OK the way it is.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/