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?

View the original article here

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Re: Beginning cocoa programming: delegates

I constructed another simple example of a delegate: I created an app with one lone NSTextField on the window.  I wanted to see if setDelegate: would work with a different widget(NSTextField v. NSWindow).  My goal was to see if I could setup a delegate using setDelegate: on an NSTextField, such that a delegate method would be called when I typed in the text field.  I  looked through the documentation, and I decided to to see if implementing this delegate method would work:

 

- (BOOL)control:(NSControl *)control textShouldBeginEditing:(NSText *)fieldEditor;

 

 

I created a new app(deleting the classes that Xcode automatically creates, as well as the instance in the MainWindow.xib window in IB), and then I created this class:

 

 

//MyDelegate.h

 

import

 

@interface MyDelegate : NSObject {

}

- (BOOL)control:(NSControl *)control

          textShouldBeginEditing:(NSText *)fieldEditor;

 

@end

 

 

//MyDelegate.m

 

@implementation MyDelegate

 

- (BOOL)control:(NSControl *)control

               textShouldBeginEditing:(NSText *)fieldEditor

{

          NSLog(@"***In delegate method...");

          return YES;

}

 

@end

 

 

1) In IB, I created an instance of MyDelegate by dragging an Object from the Library onto the MainWindow.xib window.  I entered the name MyDelegate in the TextField Identity Inspector.

 

2) In IB, I ctrl-clicked on the NSTextField, and then I dragged a connection from NSTextField's 'delegate' outlet to the MyDelegate instance(in the MainWindow.xib window).

 

3) Saved everything, build&run, and when I typed in the text field, I saw the logged message in the Debugger Console, as expected.

 

Next, I attempted to create code that uses setDelegate: to achieve the same thing as above.

 

4) In IB, I ctrl-clicked on the NSTextField and deleted the connection from the 'delegate' outlet to the MyDelegate instance.

 

5)  I made these changes to the code:

 

//MyDelegate.h

 

#import

 

@interface MyDelegate : NSObject {

 

          IBOutlet NSTextField* textField;

}

- (id)init;

- (BOOL)control:(NSControl *)control

          textShouldBeginEditing:(NSText *)fieldEditor;

 

@end

 

 

//MyDelegate.m

#import "MyDelegate.h"

 

@implementation MyDelegate

 

- (id) init

{

          if (![super init]) {

                    return nil;

          }

 

          [textField setDelegate:self];

 

          return self;

}

 

- (BOOL)control:(NSControl *)control

          textShouldBeginEditing:(NSText *)fieldEditor

{

          NSLog(@"***In delegate method...");

          return YES;

}

 

@end

 

 

6) In IB, I ctrl-clicked on the MyDelegate instance in the MainWindow.xib window, and then I dragged a connection from the outlet 'textField' to the NSTextField(in the app's main window).

 

7) I saved in IB, then build&run (save everything), and this time when I typed in the textfield, the message was not logged to the Debug Console.

 

What is the matter with setDelegate:?  Why doesn't setDelegate: succeed in setting up the delegate so that I can see the message logged to the console?

 

Thanks

View the original article here

Read More

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?

View the original article here

Read More

Re: Beginning cocoa programming: delegates

I constructed another simple example of a delegate: I created an app with one lone NSTextField on the window.  I wanted to see if setDelegate: would work with a different widget(NSTextField v. NSWindow).  My goal was to see if I could setup a delegate using setDelegate: on an NSTextField, such that a delegate method would be called when I typed in the text field.  I  looked through the documentation, and I decided to to see if implementing this delegate method would work:

 

- (BOOL)control:(NSControl *)control textShouldBeginEditing:(NSText *)fieldEditor;

 

 

I created a new app(deleting the classes that Xcode automatically creates, as well as the instance in the MainWindow.xib window in IB), and then I created this class:

 

 

//MyDelegate.h

 

import

 

@interface MyDelegate : NSObject {

}

- (BOOL)control:(NSControl *)control

          textShouldBeginEditing:(NSText *)fieldEditor;

 

@end

 

 

//MyDelegate.m

 

@implementation MyDelegate

 

- (BOOL)control:(NSControl *)control

               textShouldBeginEditing:(NSText *)fieldEditor

{

          NSLog(@"***In delegate method...");

          return YES;

}

 

@end

 

 

1) In IB, I created an instance of MyDelegate by dragging an Object from the Library onto the MainWindow.xib window.  I entered the name MyDelegate in the TextField Identity Inspector.

 

2) In IB, I ctrl-clicked on the NSTextField, and then I dragged a connection from NSTextField's 'delegate' outlet to the MyDelegate instance(in the MainWindow.xib window).

 

3) Saved everything, build&run, and when I typed in the text field, I saw the logged message in the Debugger Console, as expected.

 

Next, I attempted to create code that uses setDelegate: to achieve the same thing as above.

 

4) In IB, I ctrl-clicked on the NSTextField and deleted the connection from the 'delegate' outlet to the MyDelegate instance.

 

5)  I made these changes to the code:

 

//MyDelegate.h

 

#import

 

@interface MyDelegate : NSObject {

 

          IBOutlet NSTextField* textField;

}

- (id)init;

- (BOOL)control:(NSControl *)control

          textShouldBeginEditing:(NSText *)fieldEditor;

 

@end

 

 

//MyDelegate.m

#import "MyDelegate.h"

 

@implementation MyDelegate

 

- (id) init

{

          if (![super init]) {

                    return nil;

          }

 

          [textField setDelegate:self];

 

          return self;

}

 

- (BOOL)control:(NSControl *)control

          textShouldBeginEditing:(NSText *)fieldEditor

{

          NSLog(@"***In delegate method...");

          return YES;

}

 

@end

 

 

6) In IB, I ctrl-clicked on the MyDelegate instance in the MainWindow.xib window, and then I dragged a connection from the outlet 'textField' to the NSTextField(in the app's main window).

 

7) I saved in IB, then build&run (save everything), and this time when I typed in the textfield, the message was not logged to the Debug Console.

 

What is the matter with setDelegate:?  Why doesn't setDelegate: succeed in setting up the delegate so that I can see the message logged to the console?

 

Thanks

View the original article here

Read More