From: dblack@...
Date: 2006-01-04T00:02:04+09:00
Subject: Re: More on the fundamentals...

Hi --

On Tue, 3 Jan 2006, John Maclean wrote:

> Please have a look at the comments below to see that I'm
> understanding things correctly;
>
> #!/usr/bin/ruby
> #Tue Jan  3 14:04:28 GMT 2006
> class Greeter
>        # a new class cllaed Greeter
>        def initialize(name)
>                # creating a new method called name

There's no method called name.

>                @name = name
>                # we define a new @instance variable called name

Move the @ from @instance to name and you're set :-)

>        end
>        def say(phrase)
>                # creating a new method called phrase...

There's no method called phrase.

>                puts "#{phrase}, #{@name}"
>                # ... which uses doube quotes to substitute
>        end
> end

It seems that you're confusing instance variable assignment with
method creation.  They're unrelated.  You can, of course, write a
method that returns the current value of an instance variable:

   def name
     @name
   end

and you can even get Ruby to do it semi-automatically for you:

   attr_reader :name  # creates the above "name" method

But @name = name is just a variable assignment.

> # say hello
> g1 = Greeter.new("jayeola")
> g2 = Greeter.new("buddy")
> g3 = Greeter.new("vimmer")
> g4 = Greeter.new("slammer")
> # we have just created four new  (object) instances belonging to the class
> # Greeter. They can now use the instance variables that have been created

I would say "instances of the class Greeter".

> # above
> g1.say("Hello")
> g2.say("Wotcha")
> g3.say("Ire!")
> g4.say("Elake")

Have another look at the attr_* family of methods, and keep in mind
that they're essentially shortcuts for writing your own get-and/or-set
methods (using instance variables), and I think that part of it will
fall into place.


David

-- 
David A. Black
dblack@wobblini.net

"Ruby for Rails", from Manning Publications, coming April 2006!
http://www.manning.com/books/black