单例

import Foundation

class NetWorkingTools:NSObject {

    // func == -
    // class func == +

    // 方法一：
    /* static var onceToken: dispatch_once_t = 0; static var _instance: NetworkTools? class func shareNetworkTools() -> NetworkTools { print(onceToken) dispatch_once(&NetworkTools.onceToken,{ _instance = NetworkTools() }) return _instance! } */

    // 方法二：
    /* static let _instance: NetworkTools = NetworkTools() class func shareNetworkTools() -> NetworkTools { return _instance } override init() { print("++++++") } */

    // 方法三：
    // 如果在Swift中编写单例,推荐使用如下写法
    // 而且苹果有统一的命名规范,但凡是单例统一是用shareInstance
    static let shareInstance: NetWorkingTools = NetWorkingTools()
}