dispatch_once这个函数会只运行一次;不管多少次调用;
static DMHolidayManager *sharedInstance;
@implementation DMHolidayManager
+ (DMHolidayManager *)sharedManager{
static dispatch_once_t oneToken;
dispatch_once(&oneToken, ^{
if (sharedInstance == nil) {
sharedInstance = [[DMHolidayManager alloc] init];
}
});
return sharedInstance;
}