單例--iOS

標籤：

GCD單例：

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

 

為了防止外界通過alloc方法申請到另一塊記憶體，只產生單個執行個體，需要覆蓋父類的allocWithZone方法 需要注意安全執行緒

+(id)allocWithZone:(struct _NSZone *)zone{    @synchronized(self){        if (sharedSingleton == nil) {            sharedSingleton = [super allocWithZone:zone];        }    }    return sharedSingleton;} +(id)copyWithZone:(struct _NSZone *)zone{    return sharedSingleton;}

 

單例--iOS