Re: Understanding callbacks

[RichardK]

Have a look at Tk::UserGuide for examples of how a gui uses callbacks.

The first example is this :-

    #!/usr/bin/perl -w  
        use Tk;
        use strict;

        my $mw = MainWindow->new;
        $mw->Label(-text => 'Hello, world!')->pack;
        $mw->Button(
            -text    => 'Quit',
            -command => sub { exit },
        )->pack;
        MainLoop;

The program sets up the gui then calls MainLoop and never returns, only when the user clicks on the button will the callback -command get called.

[stevieb]

I very much appreciate everyone's feedback in this thread, but I'm replying here as this post (after reading through the docs of Tk) showed me that I wasn't really trying to understand callbacks, but as a few stated, Event Driven Programming.

I just didn't correlate the two so deeply, but now I fully understand the purpose of a callback in non-event driven apps (grep was a *great* example for me to grasp).

Although I don't have any need to do GUI programming, I am going to play around with it for a while so I can grasp this event-driven thing, as I want to fully understand how it works so perhaps one day I can incorporate some of their benefits into apps I do write on a daily basis.

Again, thanks to all the Monks who replied with such in-depth and thought-out posts to help me understand not just about callbacks, but programming at another level.

Thanks and regards,

-stevieb