Modify the return value type of canAuthenticate()

BiometricAuthentication/BiometricAuthentication/Authentication/BioMetricAuthenticator.swift

@@ -55,15 +55,24 @@ open class BioMetricAuthenticator: NSObject {
 public extension BioMetricAuthenticator {
 
     /// checks if biometric authentication can be performed currently on the device.
-    class func canAuthenticate() -> Bool {
+    class func canAuthenticate() -> CheckAuthenticateAbleResult<AuthenticationError> {
 
         var isBiometricAuthenticationAvailable = false
         var error: NSError? = nil
 
         if LAContext().canEvaluatePolicy(LAPolicy.deviceOwnerAuthenticationWithBiometrics, error: &error) {
             isBiometricAuthenticationAvailable = (error == nil)
         }
-        return isBiometricAuthenticationAvailable
+
+        if isBiometricAuthenticationAvailable,
+            error == nil {
+            return CheckAuthenticateAbleResult.success
+        } else if let err = error{
+            let authenticationError = AuthenticationError.initWithError(err as! LAError)
+            return CheckAuthenticateAbleResult.failure(authenticationError)
+        } else {
+            return CheckAuthenticateAbleResult.failure(nil)
+        }
     }
 
     /// Check for biometric authentication
@@ -87,8 +96,8 @@ public extension BioMetricAuthenticator {
         }
 
         // authenticate
-        BioMetricAuthenticator.shared.evaluate(policy: LAPolicy.deviceOwnerAuthenticationWithBiometrics, with: context, reason: reasonString, success: successBlock, failure: failureBlock)
-    }
+            BioMetricAuthenticator.shared.evaluate(policy: LAPolicy.deviceOwnerAuthenticationWithBiometrics, with: context, reason: reasonString, success: successBlock, failure: failureBlock)
+        }
 
     /// Check for device passcode authentication
     class func authenticateWithPasscode(reason: String, cancelTitle: String? = "", success successBlock:@escaping AuthenticationSuccess, failure failureBlock:@escaping AuthenticationFailure) {

BiometricAuthentication/BiometricAuthentication/Authentication/CheckAuthenticateAbleResult.swift

@@ -0,0 +1,16 @@
+//
+//  CheckAuthenticateAbleResult.swift
+//  BiometricAuthentication
+//
+//  Created by linjj on 2018/12/13.
+//  Copyright © 2018 Rushi Sangani. All rights reserved.
+//
+
+import Foundation
+
+public enum CheckAuthenticateAbleResult<T> {
+    case success
+    case failure(T?)
+}
+
+

BiometricAuthenticationExample/BiometricAuthenticationExample/ViewController.swift

@@ -34,6 +34,28 @@ class ViewController: UIViewController {
         // Set AllowableReuseDuration in seconds to bypass the authentication when user has just unlocked the device with biometric
         BioMetricAuthenticator.shared.allowableReuseDuration = 60
 
+        // check biometric authentication usable
+        let url = BioMetricAuthenticator.canAuthenticate()
+        switch url {
+
+        case .failure(let error):
+            if error == .biometryNotAvailable {
+                showErrorAlert(message: "Biometry is not available on the device or disabled in settings.")
+            } else if error == .biometryNotEnrolled {
+                showErrorAlert(message: "The user has no enrolled biometric identities.")
+            } else if error == .biometryLockedout {
+                showErrorAlert(message: "Biometry is locked because there were too many failed attempts.")
+            } else {
+                showErrorAlert(message: "unkown error")
+            }
+        case .success:
+            startAuthentication()
+
+        }
+
+    }
+
+    func startAuthentication() {
         // start authentication
         BioMetricAuthenticator.authenticateWithBioMetrics(reason: "", success: {