Swift基础篇——懒加载

懒加载

import UIKitclass ViewController: UIViewController {    // 只有外界访问到listData的时候才会去执行闭包, 然后将闭包的返回值赋值给listData    // 注意: 一定要记住闭包后面需要写上(), 代表执行闭包    lazy var listData: [String]? = {        ()->[String]        in        print("----")        return ["longshao", "guangzhou", "beijing", "shenzhen"]        }()    // 开发中这样写    lazy var listData2: [String]? = {        print("----")        return ["longshao", "guangzhou", "beijing", "shenzhen"]    }()    lazy var listData3: [String]? = self.test()    func test() -> [String]    {        print("+++")        return ["lnj1", "lmj1", "why1", "wsz1"]    }    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {        print(listData!)        print(listData)        print(listData)        print("++++++++++++++++++++++++++++")        print(listData2)        print(listData2)        print(listData2)        print("++++++++++++++++++++++++++++")        print(listData3)        print(listData3)        print(listData3)    }}