Best singleton pattern for thread safe object

Question

Whats the best pattern for singleton? I frequently use

+ (SomeManager *)shared
{
    static SomeManager * _SomeManager = nil;
    if (_SomeManager) {
        return _SomeManager;
    }

    _SomeManager = [[SomeManager alloc] init];

    return _SomeManager;
}

Is this thread safe? If not, hot to make it safe?

See http://stackoverflow.com/questions/5720029/create-singleton-using-gcds-dispatch-once-in-objective-c — Guillaume Algis, Jul 27 '13 at 12:28
Keep in mind that "singleton" and "thread-safe object" are two *entirely* different things. — Hot Licks, Jul 27 '13 at 13:37
Lazy allocation of singletons, which usually represent a handful of bytes of memory, is a degenerate pattern. Allocate your singleton in +[SomeManger initialize], guaranteed to only be called once at class load time. — Bored Astronaut, Jul 27 '13 at 15:59

score 1 · Answer 1 · edited May 23 '17 at 10:31

1

Using an example from Create singleton using GCD's dispatch_once in Objective C

+ (id)sharedInstance
{
    static dispatch_once_t once;
    static id sharedInstance;
    dispatch_once(&once, ^{
        sharedInstance = [[self alloc] init];
    });
    return sharedInstance;
}

Clear and simple. Google better next time.

edited May 23 '17 at 10:31

Community

1
1

answered Jul 27 '13 at 13:31

Mehdzor

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score 0 · Answer 2 · answered Jul 27 '13 at 13:30

I prefer to use the GCD dispatch_once method...

+ (id) sharedSomethingManager
{
    static dispatch_once_t onceQueue;
    static SomethingkManager *somethingManager = nil;

    dispatch_once(&onceQueue, ^{somethingManager = [[self alloc] init]; });
    return somethingManager;
}

Best singleton pattern for thread safe object

2 Answers2