From: Bart Masschelein <bart.masschelein@...>
Date: 2005-08-31T03:49:42+09:00
Subject: Tk Label and instance variables

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