Create singleton using GCD's dispatch_once in Objective-C

Question

If you can target iOS 4.0 or above

Using GCD, is it the best way to create singleton in Objective-C (thread safe)?

+ (instancetype)sharedInstance
{
          


        

Answer 1

To create thread safe singleton you can do like this:

@interface SomeManager : NSObject
+ (id)sharedManager;
@end

/* thread safe */
@implementation SomeManager

static id sharedManager = nil;

+ (void)initialize {
    if (self == [SomeManager class]) {
        sharedManager = [[self alloc] init];
    }
}

+ (id)sharedManager {
    return sharedManager;
}
@end

and this blog explain singleton very well singletons in objc/cocoa