avoid magic strings when converting PlatformException.code

Author: navaronbracke

lib/src/enums/mobile_scanner_error_code.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/services.dart';
 import 'package:mobile_scanner/src/mobile_scanner_controller.dart';
 
 /// This enum defines the different error codes for the mobile scanner.
@@ -24,5 +25,25 @@ enum MobileScannerErrorCode {
   permissionDenied,
 
   /// Scanning is unsupported on the current device.
-  unsupported,
+  unsupported;
+
+  /// Convert the given [PlatformException.code] to a [MobileScannerErrorCode].
+  factory MobileScannerErrorCode.fromPlatformException(
+    PlatformException exception,
+  ) {
+    // The following error code mapping should be kept in sync with their native counterparts.
+    // These are located in `MobileScannerErrorCodes.kt` and `MobileScannerErrorCodes.swift`.
+    return switch (exception.code) {
+      // In case the scanner was already started, report the right error code.
+      // If the scanner is already starting,
+      // this error code is a signal to the controller to just ignore the attempt.
+      'MOBILE_SCANNER_ALREADY_STARTED_ERROR' =>
+        MobileScannerErrorCode.controllerAlreadyInitialized,
+      // In case no cameras are available, using the scanner is not supported.
+      'MOBILE_SCANNER_NO_CAMERA_ERROR' => MobileScannerErrorCode.unsupported,
+      'MOBILE_SCANNER_CAMERA_PERMISSION_DENIED' =>
+        MobileScannerErrorCode.permissionDenied,
+      _ => MobileScannerErrorCode.genericError,
+    };
+  }
 }

lib/src/method_channel/mobile_scanner_method_channel.dart

@@ -224,37 +224,14 @@ class MethodChannelMobileScanner extends MobileScannerPlatform {
 
     Map<String, Object?>? startResult;
 
-    MobileScannerErrorCode errorCode = MobileScannerErrorCode.genericError;
-
     try {
       startResult = await methodChannel.invokeMapMethod<String, Object?>(
         'start',
         startOptions.toMap(),
       );
     } on PlatformException catch (error) {
-      // Map the error code to a MobileScannerErrorCode.
-      // The error code strings should be kept in sync with their native counterparts.
-      // Any error code that is not mapped will be treated as a generic error.
-      switch (error.code) {
-        // In case the scanner was already started, report the right error code.
-        // If the scanner is already starting,
-        // this error code is a signal to the controller to just ignore the attempt.
-        case 'MOBILE_SCANNER_ALREADY_STARTED_ERROR':
-          errorCode = MobileScannerErrorCode.controllerAlreadyInitialized;
-        // In case no cameras are available, using the scanner is not supported.
-        case 'MOBILE_SCANNER_NO_CAMERA_ERROR':
-          errorCode = MobileScannerErrorCode.unsupported;
-        // This error code should have already been handled
-        // by the _requestCameraPermission method above,
-        // but just in case, also handle it here.
-        case 'MOBILE_SCANNER_CAMERA_PERMISSION_DENIED':
-          errorCode = MobileScannerErrorCode.permissionDenied;
-        default:
-          break;
-      }
-
       throw MobileScannerException(
-        errorCode: errorCode,
+        errorCode: MobileScannerErrorCode.fromPlatformException(error),
         errorDetails: MobileScannerErrorDetails(
           code: error.code,
           details: error.details as Object?,