LAPolicy是一个枚举，它提供两个值：LAPolicyDeviceOwnerAuthenticationWithBiometrics和LAPolicyDeviceOwnerAuthentication.

LAPolicyDeviceOwnerAuthenticationWithBiometrics支持iOS8以上系统，LAPolicyDeviceOwnerAuthentication支持iOS9以上系统，LAPolicyDeviceOwnerAuthentication同时支持TouchID和设备密码认证。

使用需导入：

#import <LocalAuthentication/LocalAuthentication.h>

//判断系统版本
if (NSFoundationVersionNumber < NSFoundationVersionNumber_iOS_8_0) {
    [self showRequestError:self.view withReason:@"系统版本不支持TouchID"];
    return;
}
        
LAContext *context = [[LAContext alloc]init];
context.localizedFallbackTitle = @"输入密码";
NSError *error = nil;
        
//判断是否可以使用TouchID
if ([context canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error]) {
    [context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:@"Home键验证已有手机指纹" reply:^(BOOL success, NSError * _Nullable error) {
        if (success) {
            dispatch_async(dispatch_get_main_queue(), ^{
                messageLabel.text = @"解锁成功";
            });
        }else {
            switch (error.code) {
                case LAErrorAuthenticationFailed:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"验证失败";
                    });
                    break;
                }
                case LAErrorUserCancel:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"用户取消验证";
                    });
                    break;
                }
                case LAErrorUserFallback:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"用户选择手动输入密码";
                            });
                    break;
                }
                case LAErrorSystemCancel:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"被系统取消(如遇来电,锁屏,按了Home键等)";
                    });
                    break;
                }
                case LAErrorPasscodeNotSet:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"用户未设置密码";
                    });
                    break;
                }
                case LAErrorTouchIDNotEnrolled:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"用户未设置TouchID";
                    });
                    break;
                }
                case LAErrorTouchIDNotAvailable:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"TouchID无效";
                    });
                    break;
                }
                case LAErrorTouchIDLockout:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"多次验证失败,TouchID被锁定";
                    });
                    break;
                }
                case LAErrorAppCancel:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"被APP取消(如切换到后台)";
                    });
                    break;
                }
                case LAErrorInvalidContext:
                {
                    dispatch_async(dispatch_get_main_queue(), ^{
                        messageLabel.text = @"LAContext对象无效";
                    });
                    break;
                }
                            
                default:
                   break;
            }
       }
    }];
}else {
    messageLabel.text = @"当前设备不支持TouchID";
}