From: Timothy Hunter <TimHunter@...>
Date: 2006-12-27T23:33:16+09:00
Subject: Re: Nuby: VisualuRuby, menutest.rb example with check boxes in submenus

Jason Mayer wrote:
> I'm back to looking at visualuRuby, have two quick questions about this
> program:
> http://vruby.sourceforge.net/sample/menutest.rb
> Basically, I don't understand this line: @checking.checked = ! @
> checking.checked?
>
> I added the following which gives me the desired results.
>
> if @checking.checked?
>      @label.caption="checked"
> else
>      @label.caption="unchecked"
> end
>
> First question:
> what does '= ! @variable' do anyway?  I've never seen an example that did
> that.
> Second question:
> How can what I added be turned into a one-liner?
>
Read "! @variable" as "not @variable". The value of the expression is 
either true or false. If @variable is anything other than false or nil, 
then "! @variable" is false. If @variable is false or nil, then "! 
@variable" is true.

Use the ternary ?: operator to turn your code into a one-liner. Your 
code is equivalent to

@label.caption = @checking.checked? ? "checked" : "unchecked"