iphone - Singleton:在哪里创建实例？

Question

有人对使用...有任何偏好或意见吗

static id sharedReactor = nil;

+(id)sharedInstance {
if(sharedReactor == nil) sharedReactor = [[super allocWithZone:NULL] init];
return sharedReactor;
}

或:

static id sharedReactor = nil;

+(void)initialize {
if(sharedRandomReactor == nil) {
sharedRandomReactor = [[super allocWithZone:NULL] init];
}

+(id) sharedInstance {
    return sharedReactor;
}

在我看来，使用 +(void)initialize 似乎更优雅，我只是好奇比我更有经验的人如何看待这两种方法？

加里

Answer 1

来自Mike Ash's site这是使用 Grand Central Dispatch 的另一种方法:

+ (id)sharedWhatever
{
    static dispatch_once_t pred;
    static Whatever *whatever = nil;
    dispatch_once(&pred, ^{
        whatever = [[Whatever alloc] init];
    });
    return whatever;
}