From: Hermann Martinelli <hermann.martinelli@...>
Date: 2007-06-25T02:05:02+09:00
Subject: Re: Newbie Question Passing variables to methods

Starke wrote:
> As you can see, I pass in var1 into the method and then I change the
> value to 'test1'.  I would like to method to go back and update var1,
> so that if passed into another method it reflects the change that
> method change var_in did.  Does this make since?  Im new to
> programming.

What you want to do is a "call by reference".
What you get is a "call by value".
This is just to let you know the terminology.
Search the web for more about these concepts.

As soon as you assign a new value (object) to
your local variable in the method change(), it
will no longer point to the object passed as
argument, but instead point to a new object.
The object that was passed remains unchanged.

The code below my signature could make a lot
of things clearer. Just run it and come back
if you have questions.

Btw: You don't need to know all this to use
Ruby. So don't worry and don't forget to have
fun with this wonderful and easy programming
language.

HM




def change x
   puts "With value just passed:",
        "ID of x:     #{x.object_id}",
        "Value of x:  #{x}"
   x = 'abc'
   puts "With new value: ",
        "ID of x:     #{x.object_id}",
        "Value of x:  #{x}"
   return x
end

a = "Hallo"
puts "Before calling change():",
      "ID of a:     #{a.object_id}"
rv = change a  # return value
puts "After calling change():",
      "ID of rv:    #{rv.object_id}",
      "Value of rv: #{rv}",
      "ID of a:     #{a.object_id}",
      "Value of a:  #{a}"