From: Joel VanderWerf <vjoel@...>
Date: 2003-07-04T06:17:24+09:00
Subject: Re: FXDataTarget not updating my variable

Hans Fugal wrote:
> Lyle Johnson <lyle@users.sourceforge.net> wrote:
...
>>If this is too restrictive for your application, you might want to check 
>>out some work that Joel VanderWerf has done with his FoxTails extension 
>>for FXRuby (http://raa.ruby-lang.org/list.rhtml?name=foxtails). It takes 
>>advantage of the "observable" module (another of Joel's creations) to 
>>allow you to connect GUI components to observable attributes. This is a 
>>potentially much more powerful approach and it may offer the kind of 
>>solution you're looking for.
> 
> Looks very interesting. Indeed this is exactly the sort of thing we are
> doing.

Hans, here's how I'd write your original example using FoxTails:

==========================
#!/usr/bin/env ruby

require 'fox'
require 'foxtails'

include Fox
include FoxTails

class DataTargetWindow < FXMainWindow
   include Observable

   observable :foo

   def initialize(app)
     super(app, "Data Targets Test", nil, nil, DECOR_ALL, 20, 20, 200, 100)

     self.foo = "foo" # NOTE: "@foo = ..." will not trigger updates

     vframe = FXVerticalFrame.new(self)
     frame = FXHorizontalFrame.new(vframe)

     l = FXLabel.new(frame,"B")
     tf = FTTextField.new(frame,10,self,:foo)

     tf.dynamic = true # assuming you want foo updated while you are editing

     when_foo CHANGES do
       l.text = foo
     end

     FXButton.new(vframe,"puts").connect(SEL_COMMAND) do
       puts foo
     end

     show
   end
end

if __FILE__ == $0
   application = FXApp.new("DataTarget", "FoxTest")
   window = DataTargetWindow.new(application)
   application.create
   application.run
end
==========================

If you don't want the label to change while you are editing, just remove 
the "tf.dynamic = true".

Note that "when_foo" is not limited to the initialize method. You can 
set up observers from other methods, or even other objects:

   window = DataTargetWindow.new(application)
   window.when_foo CHANGES do |new_foo| ... end

Also, CHANGES is just a synonym for Object. You can use anything with an 
#=== method, including regexes. The match is attempted whenever the attr 
writer is called.

It would be possible to define a class FTLabel which lets you "tie" the 
label to a given observable attr, much like FTTextField works. However, 
it's easy enough to achieve the same effect with a "when" clause and the 
#text= accessor. Also, one principle of foxtails is that the initialize 
method of FXFooBar and FTFooBar are the same except for replacing the 
"tgt,sel" with an object (or a proc returning an object) and the name of 
an observable attr in that object. FXLabel doesn't have tgt,sel in its 
initialize, so there's no parallel over in foxtails land. Anyway, 
dynamically changing labels are kind of unusual.

Let me know if you have questions with FoxTails...