1. 视图控制器方法
   • – loadView:不要主动调用该方法，当访问控制器view的时候，就会调用该方法。如果要自己创建view，则需要重写该方法。
   • – viewDidLoad:当加载控制器的视图到内存时，该方法被调用。
   • – didReceiveMemoryWarning:接受内存警告消息

2. 视图控制器生命周期(生命周期的方法)
   • – viewWillAppear:
   • – viewDidAppear:
   • – viewWillDisappear:
   • – viewDidDisappear:

3. 模态推出(模态推出一定要dismiss)

4. view是懒加载的

5. 属性传值

ViewController
import UIKit

class ViewController: UIViewController {
    
    //初始化 第一个走的方法
//    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
//        //1.加载的xib文件 2.bundle(main)
//        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
//    }
//    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        //fatalError("init(coder:) has not been implemented")
    }
    
    //加载view 只会走一次
        override func loadView() {
            super.loadView()
//            //替换当前控制器的view
//            let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
//            self.view = imageView
        }
    
    
   //加载相关资源
    override func viewDidLoad() {
        super.viewDidLoad()
        //视图控制器 //UIControl子类  //手势
       let btn = UIButton(type: .system)
        btn.frame = CGRect(x: 100, y: 100, width: 50, height: 40)
        btn.addTarget(self, action: #selector(btnAction(btn:)), for: .touchUpInside)
        btn.setTitle("登录", for: .normal)
        self.view.addSubview(btn)
    }
    
    
    
    func btnAction(btn:UIButton){
        //模态推出下一个界面,一般用于注册
        let vc = SecondViewController()
        //1.要推出的下一个控制器
        //2.是否用动画
        //3.推出完成后回调  闭包表达式
        self.present(vc, animated: true){
            
        }
    }
    
    
    
    //视图将要显示在屏幕上
    //viewWillAppear会走很多次  回调时也可用
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
    }
    
    //显示在屏幕上
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
    }
    
    //视图将要从屏幕上消失
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
    }
    
    //视图已经消失
    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
    }
    
    //控制器被销毁
    deinit{
        
    }
    
    
    
    

    
    
     //接收到内存警告信息
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        
        // Dispose of any resources that can be recreated.
    }


}

SecondViewController
import UIKit

class SecondViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = UIColor.cyan
        
        let btn = UIButton(type: .system)
        btn.frame = CGRect(x: 100, y: 100, width: 50, height: 40)
        btn.addTarget(self, action: #selector(btnAction(btn:)), for: .touchUpInside)
        btn.setTitle("登录", for: .normal)
        self.view.addSubview(btn)
    }
    
    func btnAction(btn:UIButton){
        //当前页面回收回去
        self.dismiss(animated: true, completion: nil)
    
    
    }

    
    
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }