New to Carbon - how to disable a button?

Question

This should be basic, so I'm really not understanding why it doesn't work. I have a simple application with buttons on a window (made using interface builder), and an event handler for when they're clicked. One of them runs this function;
void
MainWindow::Play( TWindow* win, unsigned int x, unsigned int y )
win->SetTitle( CFSTR( "Hello" ) );
ControlRef btn = nil;
ControlID btnID = { 'bn00', 0 };
GetControlByID( (WindowRef) win, &btnID, &btn );
DisableControl( btn );
The first line is my debugging - when the button is clicked the window's title changes to "Hello" so I know it's running fine and the window pointer is correct, but the button isn't getting disabled (no errors either)
bn00 is the button's signature and 0 is it's ID, since that's what I guessed it matched up to. Is that right? if it is then what's wrong?!

Answer 1

To port a Windows app, the best strategy would be to isolate the user interface code from the rest of the app's code. Assuming the Windows code was written in C++, you would keep the non-interface C++ code and use Cocoa for the user interface. Objective C++ lets you mix C++ and Objective C code in your app. You have to give your Objective C files the extension .mm to make them Objective C++ files.
There's nothing stopping you from using Carbon, but Carbon is difficult to learn for someone new to Mac development. There are no up-to-date Carbon books so you have to rely on Apple's documentation for everything. Most people on Mac programming message boards are Cocoa developers, which makes getting answers to your questions difficult. Going with Cocoa is less painful.