Hidetoshi NAGAI
3/23/2009 8:18:00 PM
From: Cristian Achim <cristiach@yahoo.com>
Subject: ruby tkentry tkvariable with class wrappers problem
Date: Tue, 24 Mar 2009 04:43:01 +0900
Message-ID: <34100fb324f5193a1b8567f60a34eea0@ruby-forum.com>
> it doesn't work : it says that themember variable supposed to hold a
> link to the tkVariable object is nil:nilClass when i try to call the
> value member function
Hmmm...
You may be misunderstanding about a block given to <widgetclass>.new.
# And, your code has a problem about accessing a TkVariable object.
---------------------------------------------------
@files_lcoation_text=TkVariable.new
@files_location_text=""
@files_location_entry=TkEntry.new(tk_root){
textvariable @files_location_text
}.grid("row"=>0 , "column"=>1)
@files_location_text="tada"
---------------------------------------------------
Such block is evaluated with "instance_eval".
That is, at internal of the block, "self" is the widget created by
"new" method. So, @files_location_text in the block is a instance
variable of the entry widget.
There are two ways to avoid this problem.
The one is to use a local variable.
And another is to use a Hash argument.
-----<case.1>----------------------------------------------
@files_lcoation_text = txt_var = TkVariable.new("")
@files_location_entry=TkEntry.new(tk_root){
textvariable txt_var
}.grid("row"=>0 , "column"=>1)
@files_location_text.value = "tada"
-----------------------------------------------------------
-----<case.2>----------------------------------------------
@files_lcoation_text = TkVariable.new("")
@files_location_entry=TkEntry.new(tk_root, :textvariable=>@files_lcoation_text).grid(:row=>0 , :column=>1)
@files_location_text.value = "tada"
-----------------------------------------------------------
Please take attention to a scope of a variable.
--
Hidetoshi NAGAI (nagai@ai.kyutech.ac.jp)