Access to the NIB window controls

Question

I have inherited a new class from NSWindowController to implement windowDidLoad and then access to the NIB defined window controls:

- ( void ) windowDidLoad
{
   NSArray * controls = [ [ [ self window ] contentView ] subviews ];
   int i;

   NSRunAlertPanel( @"windowDidLoad", @"", @"OK", NULL, NULL );

   if( [ controls count ] == 0 )
      NSRunAlertPanel( @"no hay controles", @"", @"OK", NULL, NULL );   

   for( i = 0; i < [ controls count ]; i++ )
      NSRunAlertPanel( @"control", @"", @"OK", NULL, NULL );   
}

code execution goes fine. The NIB window is shown, but subviews has no elements. How to access the window child controls ? Thanks,

Answer 1

It seems as window is nil. How to access it from windowDidLoad ?? thanks,

Answer 2

The NIB window is shown, but subviews has no elements.

You probably forgot to hook up the window outlet to your window. When the outlet is not hooked up, the outlet property holds nil, so [self window] returns nil.

Then you send messages to nil. I say “messages” because every message to nil does nothing and returns nil, 0, or 0.0 as appropriate. That means you send the contentView message to nil, so that returns nil, which means you send the subviews message to nil, so that also returns nil.

As I said, a message to nil returns nil, 0, or 0.0; when you send the count message to controls, since controls is nil as explained in the previous paragraph, that message returns 0.

The fix is to open your nib in IB and connect your controller's window outlet to your window.

By the way, you should not use indexes to loop over NSArrays. There is a simpler, cleaner way to do it: Fast Enumeration.