From: Hidetoshi NAGAI <nagai@...>
Date: 2010-12-28T10:34:25+09:00
Subject: Re: Problems w/ Tk::Tile::Label.new scope?

From: "Joseph D." <josephdivelbiss@gmail.com>
Subject: Problems w/ Tk::Tile::Label.new scope?
Date: Tue, 28 Dec 2010 04:49:32 +0900
Message-ID: <0e3c6a7e26bda6d69a56d6ed8fa0a366@ruby-forum.com>
> non-working:
> @button = Tk::Tile::Label.new($content){image @image}.grid(:column =>
> @position, :row => 1, :sticky =>'we')

A block given to "new" method of TkWindow class (and sub-class of
TkWindow) is evaluated by "instance_eval". So, at internal of the
block, "self" denotes the created widget object.
Your "{image @image}" means "{self.image(@image)}" and the "self" is
the button widget (@button). @image is not a instance variable of the
button widget. It is the reason of why your script doesn't work.

Your trouble depends on the scope of variables. So,
--------------------------------------------------------------
Ans 1: give a hash of widget options to "new" method.
  @button = Tk::Tile::Label.new($content, :image => @image, ...).grid(:column => @position, :row => 1, :sticky =>'we')

Ans 2: use local variables (not equal to names of wiget options)
  img = @image
  @button = Tk::Tile::Label.new($content){image img; ...}.grid(:column => @position, :row => 1, :sticky =>'we')
--------------------------------------------------------------

> working method 1:
> @button = Tk::Tile::Label.new($content).grid(:column => @position, :row
> => 1, :sticky =>'we')
>     @button['image'] = @image

or "@button.image @image" or "@button.image = @image" or
"@button.configure(:image => @image, ... )".
Methods for widget options aren't shown by Object#methods method.
"method_missing" method is used to implement those method.
If you want to get the list of supported widget options,
Please use "@button.current_configinfo.keys" or
"@button.configinfo.collect{|optinfo| optinfo[0]}".

> working method 2:
> @button = Tk::Tile::Label.new($content){image @@image}.grid(:column =>
> @position, :row => 1, :sticky =>'we')
   (snip)
> Using a class variable of the class, method 2, worked, but seemed like a
> poor coding practice to me. (I am trying to learn good ways not bad
> ones)

In this case, you use a class variable as a global variable.
It is a wrong solution.
-- 
Hidetoshi NAGAI (nagai@ai.kyutech.ac.jp)
Department of Artificial Intelligence, Kyushu Institute of Technology