swift单例

gistfile1.txt

class SwiftSingleton {   
    class var shared: SwiftSingleton {   
            return Inner.instance   
    }   
   
    struct Inner {   
        static let instance: SwiftSingleton = SwiftSingleton()   
    }   
}


class SwiftSingleton {   
    class var shared: SwiftSingleton {   
        dispatch_once(&Inner.token) {   
            Inner.instance = SwiftSingleton()   
        }   
        return Inner.instance!   
    }   
    struct Inner {   
        static var instance: SwiftSingleton?   
        static var token: dispatch_once_t = 0   
    }   
       
}

+ (id)shareInstance
{
    static CRSA *_crsa = nil;   //CRSA is class name
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _crsa = [[self alloc] init];
    });
    return _crsa;
}