Question

I’m developing an iOS 4 app with latest SDK and XCode 4.2.

I have a question about delegates and how to assign/release objects to them.

My code is:

#import <Foundation/Foundation.h>
#import "SBJson.h"
#import "WebServiceDelegate.h"

@interface UserWebService : NSObject
{
    SBJsonParser* parser;
    NSURLRequest* request;
    NSMutableData* receivedData;
    NSInteger response;

    id<WebServiceDelegate> delegate;
}

@property (nonatomic, readonly) NSInteger response;

- (id)initWithDelegate:(id<WebServiceDelegate>)del;

And its implementation:

#import "UserWebService.h"

@implementation UserWebService

@synthesize response;

- (id)initWithDelegate:(id<WebServiceDelegate>)del
{
    if (self = [super init])
    {
        delegate = [del retain];
        parser = [[SBJsonParser alloc] init];
    }
    return self;
}

-(void)dealloc
{
    [parser release];
    [request release];
    [receivedData release];

    [super dealloc];
}

Is this correct?

delegate = [del retain];

And, Have I to release del at dealloc?

If I use

delegate = del;

instead of

delegate = [del retain];

I get a EXC_BAD_ACCESS on object dealloc.

In a nutshell, I’m not sure if I’m assign and releasing del object correctly.

Answer 1

When you’re using delegates, your object should not retain & release it since it does not own it.

Implement the accessor methods. In a memory-managed program, to avoid
retain cycles, the setter method should not retain or copy your
delegate.

- (id)delegate {
    return delegate;
}

- (void)setDelegate:(id)newDelegate {
    delegate = newDelegate;
}

Source