Make sure you cannot run multiple permission requests at the same time

ios/Classes/PermissionManager.swift

@@ -10,6 +10,8 @@ import Foundation
 import UIKit
 import Swift
 
+typealias PermissionRequestCompletion = (_ permissionRequestResults: [PermissionGroup:PermissionStatus]) -> ()
+
 class PermissionManager: NSObject {
     private var _strategyInstances: [ObjectIdentifier: PermissionStrategy] = [:]
     
@@ -20,7 +22,7 @@ class PermissionManager: NSObject {
         result(Codec.encodePermissionStatus(permissionStatus: permissionStatus))
     }
     
-    func requestPermission(permissions: [PermissionGroup], result: @escaping FlutterResult) {
+    func requestPermissions(permissions: [PermissionGroup], completion: @escaping PermissionRequestCompletion) {
         var requestQueue = Set(permissions.map { $0 })
         var permissionStatusResult: [PermissionGroup: PermissionStatus] = [:]
         
@@ -35,7 +37,7 @@ class PermissionManager: NSObject {
                 self._strategyInstances.removeValue(forKey: ObjectIdentifier(permissionStrategy as AnyObject))
                 
                 if requestQueue.count == 0 {
-                    result(Codec.encodePermissionRequestResult(permissionStatusResult: permissionStatusResult))
+                    completion(permissionStatusResult)
                     return
                 }
             }

ios/Classes/SwiftPermissionHandlerPlugin.swift

@@ -10,6 +10,7 @@ import UIKit
 public class SwiftPermissionHandlerPlugin: NSObject, FlutterPlugin {
     private static let METHOD_CHANNEL_NAME = "flutter.baseflow.com/permissions/methods";
     private let _permissionManager: PermissionManager = PermissionManager()
+    private var _methodResult: FlutterResult?
     
     public static func register(with registrar: FlutterPluginRegistrar) {
         let channel = FlutterMethodChannel(name: METHOD_CHANNEL_NAME, binaryMessenger: registrar.messenger())
@@ -25,11 +26,25 @@ public class SwiftPermissionHandlerPlugin: NSObject, FlutterPlugin {
                 permission: permission,
                 result: result)
         } else if call.method == "requestPermissions" {
+            if _methodResult != nil {
+                result(FlutterError(
+                    code: "ERROR_ALREADY_REQUESTING_PERMISSIONS",
+                    message: "A request for permissions is already running, please wait for it to finish before doing another request (note that you can request multiple permissions at the same time).",
+                    details: nil))
+            }
+            
+            _methodResult = result
             let permissions: [PermissionGroup] = Codec.decodePermissionGroups(from: call.arguments)
             
-            _permissionManager.requestPermission(
-                permissions: permissions,
-                result: result)
+            _permissionManager.requestPermissions(permissions: permissions) {
+                (permissionRequestResults: [PermissionGroup:PermissionStatus]) in
+                
+                if self._methodResult != nil {
+                    self._methodResult!(Codec.encodePermissionRequestResult(permissionStatusResult: permissionRequestResults))
+                }
+                
+                self._methodResult = nil
+            }
         } else if call.method == "shouldShowRequestPermissionRationale" {
             result(false)
         } else if call.method == "openAppSettings" {