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例如以下代码是实现调用5S以上设备指纹识别的代码，依照官网给出的代码，会出现识别成功后非常久才运行成功后调用的代码，逛了非常久的。才知道要将其放入主线程实现才干够。

详细代码例如以下。

1、引入类  import LocalAuthentication

//调用指纹识别函数
    func loginWithTouchID()
    {
        if((UIDevice.currentDevice().systemVersionasNSString).floatValue >= 8.0)
        {
            // Get the local authentication context.
            let context = LAContext()
            // Declare a NSError variable.
            var error: NSError?

            // Set the reason string that will appear on the authentication alert.
            var reasonString = "弹出指纹识别框时提示用户的字符串"
            // Check if the device can evaluate the policy.
            if context.canEvaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, error: &error)
            {
                context.evaluatePolicy(LAPolicy.DeviceOwnerAuthenticationWithBiometrics, localizedReason: reasonString, reply: { (success: Bool, evalPolicyError: NSError?) -> Voidin
                    dispatch_async(dispatch_get_main_queue(), { () -> Voidin //放到主线程运行。这里特别重要
                        if success
                        {
                         	//调用成功后你想做的事情   
                        }
                        else
                        {
                            // If authentication failed then show a message to the console with a short description.
                            // In case that the error is a user fallback, then show the password alert view.
                            println(evalPolicyError?.localizedDescription)
                        }
                    })
                })
            }
            else
            {
                // If the security policy cannot be evaluated then show a short message depending on the error.
                switch error!.code
                {
                caseLAError.TouchIDNotEnrolled.rawValue:
                    println("您还没有保存TouchID指纹")
                caseLAError.PasscodeNotSet.rawValue:
                    println("您还没有设置密码")
                default:
                    // The LAError.TouchIDNotAvailable case.
                    println("TouchID不可用")
                }
                // Optionally the error description can be displayed on the console.
                println(error?.localizedDescription)
                // Show the custom alert view to allow users to enter the password.
            }
        }
    }