iOS App开发中使用设计模式中的单例模式的实例解析

#import "LGManagerCenter.h"

static LGManagerCenter *managerCenter;

@implementation LGManagerCenter

+(LGManagerCenter *)sharedManager{
  if(!managerCenter)
    managerCenter=[[self allocWithZone:NULL] init];
  return managerCenter;
}

@end

#import "LGManagerCenter.h"


@implementation LGManagerCenter


+(LGManagerCenter *)sharedManager{
  static dispatch_once_t predicate;
  static LGManagerCenter * managerCenter;
  dispatch_once(&predicate, ^{
    managerCenter=[[LGManagerCenter alloc] init];
  });
  return managerCenter;
}

@end

+(instancetype)myAlloc{
  return [super allocWithZone:nil];
}

+(ZYHPayManager *)sharedMamager{
  static ZYHPayManager * manager;
  if (manager==nil) {
    manager=[[ZYHPayManager myAlloc]init];
  }
  return manager;
}

+(instancetype)alloc{
  NSAssert(0, @"这是一个单例对象，请使用+(ZYHPayManager *)sharedMamager方法");
  return nil;
}
+(instancetype)allocWithZone:(struct _NSZone *)zone{
  return [self alloc];
}
-(id)copy{
  NSLog(@"这是一个单例对象，copy将不起任何作用");
  return self;
}
+(instancetype)new{
  return [self alloc];
}