use dispatch_once
+ (instancetype)instance { static PSDrawerManager *manager = nil; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ manager = [[PSDrawerManager alloc] init]; }); return manager; }
use dispatch_once
+ (instancetype)instance { static PSDrawerManager *manager = nil; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ manager = [[PSDrawerManager alloc] init]; }); return manager; }