Beginning cocoa programming: delegates

Xcode 3.2.2

Mac OS X 10.6.8

Cocoa Programming for Mac OS X (third edition)

Chapter 6: Helper objects

 

What happened to the forum software?  I can't quote text/code anymore.

 

I'm trying to create a simple delegate for an NSWindow.  The delegate implements this method:

 

- (NSSize)windowWillResize:(NSWindow *)sender toSize:(NSSize)frameSize;

 

I can get my delegate to work if I use Interface Builder to connect my app's main(and only) window to an instance of my object(which appears in the MainMenu.xib inspector in IB).  However, I cannot get a delegate to work if I call setDelegate: on my app's main window.  In the book, there is one example where they use setDelegate: to setup the delegate object.  There is another example where they use IB to hook up the delegate.  The only distinction I can detect between the two examples is that in the one that employs setDelegate:, the delegate-or is not a widget, and in the one that uses IB to make the connection, the delegate-or is a widget.

 

This is the code that I used to try and programmatically set up a delegate:

 

//AppController.h

 

#import

 

@interface AppController : NSObject {

 

  IBOutlet NSWindow* window;

}

- (id)init;

 

 

@end

 

 

 

//AppController.m

 

#import "AppController.h"

#import "MyDelegate.h"

 

@implementation AppController

 

- (id)init

{

 

  if (![super init]) {

  return nil;

  }

 

  MyDelegate* aDelegate = [[MyDelegate alloc] init];

  [window setDelegate:aDelegate];

 

  return self;

}

 

 

@end

 

 

 

//MyDelegate.h

 

#import

 

@interface MyDelegate : NSObject {

 

}

- (NSSize)windowWillResize:(NSWindow *)sender toSize:(NSSize)frameSize;

 

 

@end

 

 

 

//MyDelegate.m

 

#import "MyDelegate.h"

 

 

@implementation MyDelegate

 

 

- (NSSize)windowWillResize:(NSWindow *)sender

                         toSize:(NSSize)frameSize

{

     frameSize.height = 2 * frameSize.width;

     return frameSize;

}

 

 

@end

 

 

In IB, I went into the Library, and I dragged an Object to the MainMenu.xib window/inspector, and I named it AppController.  Then I dragged a connection from the AppController outlet named 'window' to the NSWindow.  When I build&run my code, I can resize the window to any size--the window size is not constrained to a 2:1 ratio. That is not the result I expect: I expect the window size to maintain a 2:1 ration. If I set an object's delegate, then when the event occurs, the object should grab the delegate and use it to call the delegation methods; there is nothing more I should have to do in my code.  What am I not understanding about cocoa delegates?

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