From: Morton Goldberg <m_goldberg@...>
Date: 2007-11-24T07:00:48+09:00
Subject: Re: Class variable as parameter

On Nov 23, 2007, at 4:20 PM, Filipe wrote:

> I have the following situation:
>
> class MyClass
>    def setVar(var,varValue)
>       var=varValue
>    end
>
>    def initialize
>        @myVar=0
>        setVar(@myVar,1)
>        puts(@myVar.to_s)
>    end
> end
>
> test = MyClass.new
>
> Unfortunately, this piece of code is returning 0 instead of the 1 I
> would expect. Is there anything I could do?

Your call to setVar can not change the value of an variable. Only  
values of variables are passed in Ruby, not the variables themselves.

    def setVar(var,varValue)
       var=varValue # <-- this is the same as: return varValue
    end

    def initialize
        @myVar=0
        setVar(@myVar,1) # <-- at this point this is the same as:  
setVar(0,1)
        puts(@myVar.to_s)
    end

Ruby has a built-in method, Object#instance_variable_set that you can  
use for situations where you need to assign by name, so you don't  
need to define it for any derived class. Also, Ruby can define  
accessor methods for you:

class MyClass
    attr_accessor :myVar
    def initialize
        @myVar=0
        self.myVar = 1
        puts myVar # <-- to_s not needed; puts applies to_s to objects
    end
end
test = MyClass.new

This will output 1 and may be what you are looking for.

Regards, Morton