From: Bart Masschelein <bart.masschelein@...>
Date: 2005-08-31T03:53:02+09:00
Subject: Re: Tk Label and instance variables

Oh, and of course I could get around with the following, but I would 
like to know why the instance variable appears to be not initialized 
inside the TkLabel initialization.

    value3 = @value
   
    TkLabel.new(root) do
      text "#{value3}"
      pack { padx 15 ; pady 15; side 'left' }
    end  

Bart Masschelein wrote:

> Hello all,
>
> Below is a small piece of test code for a label using Tk. I try to set 
> a label using an instance variable, and one using a local variable. 
> The label with the local variable shows correctly in the window, the 
> one with the instance variable doesn't. I get a warning: instance 
> variable @value not initialized. Although the puts in between proves 
> differently. What is the magic between all of this?
>
> I tried adding value to attr_reader, but that didn't solve anything. 
> Not that I was expecting it to.
>
> As you probably can see, I come from a C/C++ background, and am 
> probably missing some Ruby fundamentals to solve this. My collection 
> of example scripts is rather small for the moment, and hence is also 
> my experience. So any directions are welcome.
>
> gr.b.
>
>
> class LabelTest
>  def initialize(value)
>    @value = value
>  end
>
>  def run
>    root = TkRoot.new { title "Label test" }
>           puts @value
>           TkLabel.new(root) do
>      text "#{@value}"
>      pack { padx 15 ; pady 15; side 'left' }
>    end
>       value2 = 200
>       TkLabel.new(root) do
>      text "#{value2}"
>      pack { padx 15 ; pady 15; side 'left' }
>    end         Tk.mainloop
>  end
> end
>
> test = LabelTest.new(100)
> test.run
>
>
>
>