单例在swift中的正确姿势

---

1、OC写法

+ (instanceType)sharedSoundTools {
    static EFSoundTools *instance = nil;
    static dispatch_once_t onceToken = 0;
    dispatch_once(&onceToken, ^{
        instance = [[self alloc] init];
    });
    return instance;
}

2、仿OC写法

class EFSoundTools: NSObject {
        static var instance: EFSoundTools?
        static var oneToken: dispatch_once_t = 0
        class func sharedSoundTools() -> EFSoundTools {
        dispatch_once(&oneToken) { () -> Void in
            instance = EFSoundTools()
        }
        return instance!
    }
}

3、swift写法

static let sharedSoundTools = EFSoundTools()

4、需要自定义构造函数写法

static let sharedTools: EFNetworkTools = {
    let baseURL = NSURL(string: "https://api.weibo.com/")
    let tools = EFNetworkTools(baseURL: baseURL)
    return tools
}()