swift 中的单例

今天忽然想写个单例不知道咋写了，所以想想还是记录一下吧。

• OC版本写法一(这种写法不算是太严谨)

@implementation MyPeter
+ (id)sharedManager {
    static MyPeter * staticInstance = nil;
    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{
        staticInstance = [[self alloc] init];
    });
    return staticInstance;
}
@end

• OC版本写法二(推荐这种写法)

static MyPeter * staticInstance = nil;
@implementation MyPeter
+(MyPeter *)sharedManager{
    return [[self alloc] init];
}
- (instancetype)init{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        staticInstance = [super init];
    });
    return staticInstance;
}

+(instancetype)allocWithZone:(struct _NSZone *)zone{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        staticInstance = [super init];
    });
    return staticInstance;
}


- (nonnull id)copyWithZone:(nullable NSZone *)zone{
    return staticInstance;
}
-(nonnull id)mutableCopyWithZone:(nullable NSZone *)zone{
    return staticInstance;
}




@end

• swift版本写法一（swift 1.2之前版本写法）

  class var shared : MyPeter {
          struct Static {
                static let sharedInstance : MyPeter = MyPeter()
            }
            return Static.sharedInstance
        }

• swift版本写法二（swift 1.2之前版本写法）

private let sharedInstance = MyPeter()
class  MyPeter: NSObject {
 class var shared : MyPeter {
        return sharedInstance
    }
 
}

• swift版本写法三（没有特殊要求推荐使用这种写法）

class MyPeter  {
    static let shared = MyPeter()
    private init() {}
}