简介

iPhone 5s~iPhone 8都可以通过指纹进行解锁，省去了反复输入密码的繁琐程序，这个就是Touch ID指纹识别技术。在iOS 8以后，Apple也开放了Touch ID的API给开发者，因此很多App也引入了这个新的登录方式。Face ID实现过程与Touch ID基本相同，后期也会再做补充

开发应用

• 要实现指纹识别的功能需要引入LocalAuthentication框架
• 首先我们需要判断目前设备是否支持Touch ID功能

func canEvaluatePolicy(_ policy: LAPolicy, error: NSErrorPointer) -> Bool

• LAPolicy有两个值，分别是deviceOwnerAuthenticationWithBiometrics和deviceOwnerAuthentication
• deviceOwnerAuthenticationWithBiometrics：用手指指纹去验证,iOS8.0以上可用
• deviceOwnerAuthentication：使用TouchID或者密码验证,默认是错误三次指纹或者锁定后,弹出输入密码界面iOS 9.0以上可用

• 开始指纹验证

func evaluatePolicy(_ policy: LAPolicy, localizedReason: String, reply: @escaping (Bool, Error?) -> Void)

主要代码

    func evaluate(reason: String, completed: @escaping (_ isSuccess: Bool)->())  {
        //记录是否开启Touch ID
        var canTouchID = true
        canTouchID = content.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error)

        guard canTouchID else {
            completed(false)
            return
        }
        //本地认证上下文联系对象，每次使用Touch ID功能都要重新初始化
        content = nil
        content = LAContext()

        guard let content = content else { return }
        //调起Touch ID验证弹框
        content.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: “指纹验证登录”) {
            (success, error) in
            //成功与失败进行相应的操作
            if success {
                completed(true)
            }else {
                completed(false)
                print("\(error!)")
                if let errorCode = LAError.Code(rawValue: (error! as NSError).code) {
                  switch errorCode
                    //对应errorCode的相应操作
                    ……
                }
            }
        }
    }

localizedReason：用于设置提示语，表示为什么要使用Touch ID

常见erro描述

• 在模拟器上运行结果

Error Domain=com.apple.LocalAuthentication Code=-1000 "Simulator is not supported." 
UserInfo=0x7ffe604b0790 {NSLocalizedDescription=Simulator is not supported.

• 在有TouchID 的功能下，没有设置TouchID的运行结果

Error Domain=com.apple.LocalAuthentication Code=-7 "No fingers are enrolled with Touch ID." 
UserInfo=0x170075fc0 {NSLocalizedDescription=No fingers are enrolled with Touch ID.

• 连续三次指纹识别错误

Error Domain=com.apple.LocalAuthentication Code=-1 "Aplication retry limit exceeded." 
UserInfo=0x1740797c0 {NSLocalizedDescription=Aplication retry limit exceeded.}

• 用户在Touch ID对话框中点击了取消按钮

Error Domain=com.apple.LocalAuthentication Code=-2 "Canceled by user." 
UserInfo=0x17006c780 {NSLocalizedDescription=Canceled by user.

• Touch ID三次校验失败

Error Domain=com.apple.LocalAuthentication Code=-1 "Application retry limit exceeded." 
UserInfo={NSLocalizedDescription=Application retry limit exceeded.}

• Touch ID多次校验失败

Error Domain=com.apple.LocalAuthentication Code=-8 "Biometry is locked out." 
UserInfo={NSLocalizedDescription=Biometry is locked out.

参考文章
https://www.jianshu.com/p/aef5a506311b
https://juejin.im/entry/59795ee95188253e000a74c3