Swift 懒加载

//
//  ViewController.swift
//  懒加载
//
//  Created by nanakon on 17/3/11.
//  Copyright © 2017年 nanakon. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    
    // 懒加载 用到时才加载 多次使用只加载一次
    // 程序一启动就创建了这个数组占据内存空间
    // var names : [String] = ["why", "lmj"]
    
    //lazy var names : [String] = ["why", "lmj"]

    lazy var names : [String] = {
        let names = ["why", "lmj"]
        
        print("用到names时加载names")
        
        return names
    }()
    
    //lazy var btn : UIButton = UIButton()
    
    lazy var btn : UIButton = {
        let btn = UIButton()
        btn.setTitle("按钮", for: .normal)
        return btn
    }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        print(names)
        print(btn)
    }
}