From: Ken Bloom <kbloom@...>
Date: 2009-08-05T08:08:20+09:00
Subject: Re: QtRuby Questions: Why does

On Wed, 05 Aug 2009 06:50:22 +0900, Matthew Borgeson wrote:
> My current goal is to simply have the lineEdit3 field "automagically"
> display the word "fudge" whenever a number is simply entered into
> lineEdit1, I have looked at the Rapid GUI Development Fridays book, The
> Ruby Way, and various online tutorials to help me with this to no avail.
> 
> require 'Qt'
> 
> class Form1 < Qt::Widget
> slots
>     attr_reader :textLabel1
>     attr_reader :textLabel2
>     attr_reader :textLabel3
>     attr_reader :pushButton1
>     attr_reader :lineEdit1
>     attr_reader :lineEdit2
>     attr_reader :lineEdit3

#I snipped the extra stuff that was irrelevant to the example.
#Please learn to make minimal examples.

def initialize

#somewhere deep in initialize
> 
> #start my connections
> Qt::Object.connect(@lineEdit1, SIGNAL("textChanged(const QString &)"),
>                    @lineEdit3, SLOT('update(const QString &)') )

end #I snipped the extra stuff

> 
> #start my slot methods
>   def update
>     @lineEdit3.setText( trUtf8("fudge"))
>   end
> #end my slot methods

> Here is the error message I get when I try to run it:
> 
> ruby -KA -C"/home/hujraad/Desktop/sum" -I"/home/hujraad/Desktop/sum/."
> "sum.rb"
> QObject::connect: No such slot Qt::LineEdit::update(const QString&)
> QObject::connect:  (sender name:   'lineEdit1') QObject::connect: 
> (receiver name: 'lineEdit3') *** Exited normally ***
> 
> 
> I believe I have the connections in correctly, as I have already
> practiced that with other connections. Have I improperly syntaxed the
> update() method?

When you call connect as you did with the signature (CONTROL, SIGNAL, 
CONTROL, SLOT), then the slot is called on the second control, as though 
you had called @lineEdit3.update("foobar")

You're trying to call Form1#update, and the simplest way to do that is 
use a block as the code to call. connect accepts a block like so:

@lineEdit1.connect(SIGNAL("textChanged(const QString &)")) do |thestr|
  lineEdit3.setText( trUtf8("fudge"))
end

Once you know how to do that, you can use method(:update) to get a handle 
to the update method on the current object, then using the unary & 
operator to treat it like a block, as follows:

@lineEdit1.connect(SIGNAL("textChanged(const QString &)"),
  &method(:update))

-- 
Chanoch (Ken) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/