ups!

A continuación veremos como crear una clase singleton en objective-c.

Un singleton es una clase con una única instancia. Puede servirnos para guardar variables globales de la aplicación.

MySingletonInstance.h

#import <Foundation/Foundation.h>
@interface MySingletonInstance : NSObject{
}
@property (nonatomic,retain) NSString *myString;
@property (nonatomic,retain) NSMutableArray *myArray;
+ (MySingletonInstance *) instance;
@end

MySingletonInstance.m

#import "MySharedSingleton.h"
@implementation MySharedSingleton
@synthesize myArray, myString;

static MySingletonInstance *sharedSingletonInstance = nil;

+ (FilterParams *) instance {
    @synchronized(self) {
        if(sharedSingletonInstance == nil) sharedSingletonInstance = [[self alloc] init];
    }
    return sharedSingletonInstance;
}

+ (id)allocWithZone:(NSZone *)zone {
    @synchronized(self) {
        if(sharedSingletonInstance == nil) {
            sharedSingletonInstance = [super allocWithZone:zone];
            return sharedSingletonInstance;
        }
    }
    return nil;
}

- (id) copyWithZone:(NSZone *)zone {
    return self;
}

- (id) retain {
    return self;
}

- (unsigned) retainCount {
    return UINT_MAX;
}

- (void) dealloc {
    [super dealloc];
    [myArray release];
    [myString release];
}

- (id) autorelease {
    return self;
}

Como llamar al singleton desde otra clase

MySingletonInstance *msi = [MySingletonInstance instance];
msi.myArray = self.myOtherArray;
msi.myString = self.myOtherString;