Question

I’m understanding how delegates work, had gone trough some examples, but now with a basic app for testing, it seems i haven’t yet got it,

here my code:

Class defining protocol > *.h

#import <Foundation/Foundation.h>
@protocol protoPerra <NSObject>

-(void) dimeTuNombre:(NSString *) s;
@end

@interface MyClassic : NSObject {
id<protoPerra> _delegate;  
}
@property (assign) id<protoPerra> delegate;
@end

Class implementing protocol> *.m

#import “MyClassic.h”

@implementation MyClassic
@synthesize delegate = _delegate;
- (id)init
{
self = [super init];
if (self) {
    // Initialization code here.
    [[self delegate] dimeTuNombre:@"pinguete"];
 }

return self;
}
-(void) dealloc {
[_delegate release];
_delegate = nil;
[super dealloc];
}
@end

Class Adopting protocol:

#import “MyClassic.h”
@interface MainViewController : UIViewController (protoPerra)

.m

#import "MainViewController.h"

  @implementation MainViewController
  -(void) dimeTuNombre {
   NSLog(@"ss9!! tkt");
   }
   - (void)viewDidLoad {
[super viewDidLoad];

UILabel *lava = [[[UILabel alloc] initWithFrame:CGRectMake(30, 100, 100, 20)] autorelease];
lava.text = @"lava ss9";
[self.view addSubview:lava];

MyClassic *pirr = [[[MyClassic alloc] init ] autorelease];
[pirr setDelegate:self];
 }
 -(void) dimeTuNombre:(NSString *)s {
   NSLog(@"%@",s);
  }
  @end

so what is missing in this simple example to make it work with my delegate?

thanks a lot!

Please note i have used () insted of the <> [in the .h of the adopting class] as if i use the Chevrons, the code disappears

Answer 1

You call the delegate method (dimeTuNombre:) in MyClassic init, but the delegate is not set yet, so you either need to rethink when to call dimeTuNombre:, or refactor the MyClassic class to have a constructor like

-(id)initWithDelegate:(id<protoPerra>)delegate

instead of just simple init.

To clarify, in your current code you set the delegate in MainViewController.h when you do [pirr setDelegate:self]; – which sets the value “delegate” of the property of MyClassic to the current instance of MainViewController. Note that when you call MyClassic’s init, the delegate isn’t set yet, so the [[self delegate] dimeTuNombre:@”pinguete”]; call does nothing (delegate is nil at that point).

You could change your MyClassic constructor as follows:

-(id)initWithDelegate:(id<protoPerra>)aDelegate
{
self = [super init];
if (self) {
    _delegate = aDelegate;
    // Initialization code here.
    [[self delegate] dimeTuNombre:@"pinguete"];
 }

return self;

}

Then instead of this:

MyClassic *pirr = [[[MyClassic alloc] init ] autorelease];
[pirr setDelegate:self];

You will do this:

MyClassic *pirr = [[[MyClassic alloc] initWithDelegate:self ] autorelease];

This will work, but note that usually delegates are used for notifications of various kinds – like a button reporting it was clicked or a socket says it has received some data.