From: Henning Bekel <h.bekel@...>
Date: 2008-09-16T08:07:47+09:00
Subject: Re: New to Ruby...help needed

Phillip Prentice wrote:

> Hi,
> 
> I am in the process of teaching myself Ruby and so far its great,
> however, I am coming from a procedural background and the concept of
> objects/classes are a little difficult for me to put into action. Is it
> possible to have your object execute code when it is first created?
> Perhaps some sample code and an example of what I want is needed.
> 
> Here is my desired goal:
> 
> x = SingleInst.new("TEST<5>")
> puts x.name returns 'TEST<5>"
> puts x.start_index returns '5'
> 
> Here is my code:
> 
> class Sig
> attr_accessor :name
> def initialize(name)
> @name = name
> end
> def name
> return @name
> end
> def set_name(name)
> @name = name
> end
> end
> 
> class Normal < Sig
> attr_accessor :name, :type
> def initialize(name)
> @name = name
> @type = "normal"
> end
> def to_s
> @name + "\n" + \
> @type + "\n"
> end
> def get_type
> return @type
> end
> 
> end
> 
> class SingleInst < Sig
> attr_accessor :name, :type, :start_index
> def initialize(name)
> @name = name
> @type = "SingleInst"
> @start_index = ""
> end
> 
> def set_start_index(name)
> ##Something here
> end
> 
> def get_start_index
> return @start_index
> end
> 
> end
> 
> I want the SingleInst object to automatically parse the name and grab
> the digit enclosed by '<>' and set to start_index when you created a new
> SingleInst object. Is this possible or is there a better way to
> accomplish this?
> 
> Thanks,
> 
> Phillip

Just do anything you need to initialize the object in the initialize
function, that's what it's used for.

Here's a class that does what you described:

class SingleInst
  attr_accessor :name, :start_index

  def initialize(name)
    @name = name
    # get the digit using a regexp...
    @name =~ /<(\d)>/
    @start_index = $1.to_i
  end
end

x = SingleInst.new("foo <5>")
puts x.start_index
puts x.name

You don't need to define setters and getters like that if you're using
attr_accessor.
I don't know what all that inheritance is supposed to do, put you should
probably read up on the super() method as well.

Henning