MVVM簡介:
Model: 用來表示需要的數(shù)據(jù)，不包含邏輯
View：與用戶直接交互窒升，只需處理觸發(fā)事件后的轉(zhuǎn)發(fā)缀遍，和告訴他如何顯示
ViewModel：跟蹤view的事件，處理model層傳遞的數(shù)據(jù)饱须；公開方法域醇、屬性，讓view保持最新的狀態(tài)
以下示例中：如有model蓉媳，可用來容納登錄信息

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狀態(tài)變更之后譬挚，ViewModel 可通過委托代理或閉包通知view重新加載視圖。
此處用的是閉包
LoginView代碼：

    @IBOutlet weak var phoneTfield: UITextField!
    @IBOutlet weak var verCodeTfield: UITextField!
    @IBOutlet weak var verBtn: UIButton!
    @IBOutlet weak var loginBtn: UIButton!
    var vm:LoginViewModel = LoginViewModel()
    var viewModel: LoginViewModel {
        set {
            vm = newValue
            weak var weakself = self
            vm.reloadLoginColor = {(loginValid) in
                weakself?.loginBtn.backgroundColor = weakself?.vm.loginBackgroundColor
                weakself?.loginBtn.isEnabled = !loginValid
            }
            vm.reloadVerColor = {(verBtnValid,title) in
                weakself?.verBtn.layer.borderColor = weakself?.vm.verBtnBorderColor?.cgColor
                weakself?.verBtn.setTitle(title, for: .normal)
                weakself?.verBtn.setTitleColor(weakself?.vm.verBtnBorderColor, for: .normal)
                weakself?.verBtn.isEnabled = !verBtnValid
            }
        }
        get {
            vm
        }
    }

override func awakeFromNib() {
        phoneTfield.addTarget(self, action: #selector(phonetfieldChange(textfield:)), for: UIControl.Event.editingChanged)
        verCodeTfield.addTarget(self, action: #selector(vertfieldChange(textfield:)), for: UIControl.Event.editingChanged)
         
    }

   @objc func phonetfieldChange(textfield: UITextField) {
        viewModel.phoneTextfieldChanged(textfield: textfield)
    }
    @objc func vertfieldChange(textfield: UITextField) {
        viewModel.verTextfieldChanged(textfield: textfield)
    }
    @IBAction func verCodeBtnClick(_ sender: UIButton) {
        viewModel.clickVerCode(btn: sender)
    }
    @IBAction func loginBtnClick(_ sender: UIButton) {
        viewModel.login()
    }
    deinit {
        viewModel.clearTimer()
    }

ViewModel 中暴露的屬性必須是與View需要的相匹配
LoginViewModel代碼：

class LoginViewModel: NSObject {
    var loginHome : (()->())?
    var reloadLoginColor : ((Bool)->())?
    var reloadVerColor : ((Bool,String)->())?
    private var timer: Timer?
    private var seconds: Int = 60
    private var phoneStr: String?
    private var verCodeStr: String?
    private var loginValid = true
    private var verBtnValid = true
    private var isCountDownn: Bool = false//記錄是否正在倒計時
    var loginBackgroundColor: UIColor? {
        loginValid ? .lightGray : UIColor(red: 0.04, green: 0.71, blue: 1, alpha: 1)
    }
    var verBtnBorderColor: UIColor? {
        verBtnValid ? .lightGray : UIColor(red: 0.04, green: 0.71, blue: 1, alpha: 1)
    }
    //登錄
    func login(){
        guard let str = phoneStr,str.count == 11  else {
            print("請輸入手機號")
            return
        }
        guard let str = verCodeStr,str.count == 6  else {
            print("請輸入驗證碼")
            return
        }
        loginHome?()//使用delegate或閉包都可以
    }
    //獲取驗證碼
    func clickVerCode(btn: UIButton){
        verBtnValid = true
        isCountDownn = true
        timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(countDownGetCode), userInfo: nil, repeats: true)
        RunLoop.main.add(timer!, forMode: .common)
    }
    //倒計時
    @objc func countDownGetCode(){
        seconds -= 1
        if seconds == 0 {
            seconds = 60
            verBtnValid = false
            isCountDownn = false
            reloadVerColor?(verBtnValid,"獲取驗證碼")
            clearTimer()
        }else{
            reloadVerColor?(verBtnValid,String(seconds)+"s")
        }
    }
    func clearTimer() {
        if (timer != nil) {
            timer?.invalidate()
            timer = nil
        }
    }
    //監(jiān)聽手機號輸入框
    func phoneTextfieldChanged(textfield: UITextField) {
        if let str = textfield.text,str.count > 11 {
            let phoneIndex = str.index(str.startIndex, offsetBy: 11)
            textfield.text = String(str[str.startIndex..<phoneIndex])
        }
        phoneStr = textfield.text
        loginValid = (phoneStr?.count ?? 0) == 11 && (verCodeStr?.count ?? 0) == 6 ? false : true
        reloadLoginColor?(loginValid)
        if !isCountDownn {
            //倒計時完成才能再一次獲取驗證碼
            verBtnValid = (phoneStr?.count ?? 0) == 11 ? false : true
            reloadVerColor?(verBtnValid,"獲取驗證碼")
        }
    }
    //監(jiān)聽驗證碼輸入框
    func verTextfieldChanged(textfield: UITextField) {
        if let str = textfield.text,str.count > 6 {
            let phoneIndex = str.index(str.startIndex, offsetBy: 6)
            textfield.text = String(str[str.startIndex..<phoneIndex])
        }
        verCodeStr = textfield.text
        loginValid = (phoneStr?.count ?? 0) == 11 && (verCodeStr?.count ?? 0) == 6 ? false : true
        reloadLoginColor?(loginValid)
    }
    

}

ViewController(在MVVM中也可稱為View)代碼：

class ViewController: UIViewController {
    var viewModel: LoginViewModel = LoginViewModel()
    lazy var loginv: LoginView = {
        let view = LoginView.loadFromNib()
        view.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.size.width, height: UIScreen.main.bounds.size.height)
        return view
    }()
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(loginv)
        loginv.viewModel = viewModel
        weak var weakself = self
        viewModel.loginHome = {() in
            weakself?.present(HomeViewController(), animated: true) {
                
            }
        }
    }
}