Swift Learning Daily Tip (6) Single case

近日，在翻看以前写过的一些OC应用的时候，看到了OC的单例，然后暮然想要试着写一写Swift下的单例，于是，在经过一番波折后，终于将Swift下的单例写了出来。

A single example implementation under OC

栗子:+ (instancetype)sharedNetworkTools {    //定义一个任意类型的静态实例    static id instance;    static dispatch_once_t onceToken;    // 第一次进入dispatch_once中，onceToken == 0       // 进入过一次后， onceToken == -1    dispatch_once(&onceToken, ^{        instance = [[self alloc] init];    });    return instance;}

OC under the single case everyone has written memorized, so today I will take you to imitate OC in the way of writing a swift under the single example implementation

Single example under Swift 1. Modeled OC version

//定义一个全局的静态变量static var instance: NetworkTools?//由于在Swift中，闭包内部不能写static函数，所以，只能放在外面实现啦！static var onceToken: dispatch_once_t = 0// 全局的访问点class func sharedNetworkTools() -> NetworkTools {    dispatch_once(&onceToken, { () -> Void in       self.instance = NetworkTools()    })    return instance!}

What do you think? Does it look like OC and its similar? The soup I suggest you can forget the code, according to your idea to write the swift version of the Singleton, you will find that it implies some small pits ~
Below, the small soup I bring to you under swift Special Single example implementation solution ~ Soup I mean love oh ~ Wow Quack!

2.Swift Featured Edition

// 定义一个私有的静态成员private static let instance = NetworkTools()class func sharedNetworkTools() -> NetworkTools {    return instance}

is not good simple!!!
In Swift, it let is thread-safe and, as a constant, is stored in a constant area, and instance = NetworkTools() it is lazy-loaded, and will not run until the first call.
Well, today's knowledge sharing is here ~ Welcome to the small soup blog to put forward valuable suggestions ha ~ attached to the GitHub address Https://github.com/SarielTang, interested in helping a little bit like AH ~

Swift Learning Daily Tip (6) Single case