Add Set External ID

• Adds functions to set an external ID for a user so that developers can use their own internal userID's with OneSignal

Author: Nightsd01

example/lib/main.dart

@@ -14,6 +14,7 @@ class MyApp extends StatefulWidget {
 class _MyAppState extends State<MyApp> {
   String _debugLabelString = "";
   String _emailAddress;
+  String _externalUserId;
   bool _enableConsentButton = false;
 
   // CHANGE THIS parameter to true if you want to test GDPR privacy consent
@@ -141,6 +142,21 @@ class _MyAppState extends State<MyApp> {
     });
   }
 
+  void _handleSetExternalUserId() {
+    print("Setting external user ID");
+    OneSignal.shared.setExternalUserId(_externalUserId);
+    this.setState(() {
+      _debugLabelString = "Set External User ID";
+    });
+  }
+
+  void _handleRemoveExternalUserId() {
+    OneSignal.shared.removeExternalUserId();
+    this.setState(() {
+      _debugLabelString = "Removed external user ID";
+    });
+  }
+
   void _handleConsent() {
     print("Setting consent to true");
     OneSignal.shared.consentGranted(true);
@@ -285,12 +301,40 @@ class _MyAppState extends State<MyApp> {
                     new OneSignalButton("Post Silent Notification",
                         _handleSendSilentNotification, !_enableConsentButton)
                   ]),
+                  new TableRow(children: [
+                    new TextField(
+                      textAlign: TextAlign.center,
+                      decoration: InputDecoration(
+                          hintText: "External User ID",
+                          labelStyle: TextStyle(
+                            color: Color.fromARGB(255, 212, 86, 83),
+                          )),
+                      onChanged: (text) {
+                        this.setState(() {
+                          _externalUserId = text == "" ? null : text;
+                        });
+                      },
+                    )
+                  ]),
+                  new TableRow(children: [
+                    Container(
+                      height: 8.0,
+                    )
+                  ]),
+                  new TableRow(children: [
+                    new OneSignalButton(
+                        "Set External User ID", _handleSetExternalUserId, !_enableConsentButton)
+                  ]),
+                  new TableRow(children: [
+                    new OneSignalButton(
+                        "Remove External User ID", _handleRemoveExternalUserId, !_enableConsentButton)
+                  ]),
                   new TableRow(children: [
                     new Container(
                       child: new Text(_debugLabelString),
                       alignment: Alignment.center,
                     )
-                  ])
+                  ]),
                 ],
               ),
             ),

ios/Classes/OneSignalPlugin.m

@@ -126,6 +126,10 @@ - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
         [self logoutEmail:call withResult:result];
     } else if ([@"OneSignal#didSetNotificationOpenedHandler" isEqualToString:call.method]) {
         [self didSetNotificationOpenedHandler];
+    } else if ([@"OneSignal#setExternalUserId" isEqualToString:call.method]) {
+        [OneSignal setExternalUserId:call.arguments[@"externalUserId"]];
+    } else if ([@"OneSignal#removeExternalUserId" isEqualToString:call.method]) {
+        [OneSignal removeExternalUserId];
     } else {
         result(FlutterMethodNotImplemented);
     }

lib/onesignal.dart

@@ -262,6 +262,18 @@ class OneSignal {
     return await _channel.invokeMethod("OneSignal#logoutEmail");
   }
 
+  /// OneSignal allows you to set a custom ID for your users. This makes it so that
+  /// if your app has its own user ID's, you can use your own custom user ID's with
+  /// our API instead of having to save their OneSignal user ID's.
+  Future<void> setExternalUserId(String externalId) async {
+    return await _channel.invokeMethod("OneSignal#setExternalUserId", {'externalUserId' : externalId});
+  }
+
+  /// Removes the external user ID that was set for the current user.
+  Future<void> removeExternalUserId() async {
+    return await _channel.invokeMethod("OneSignal#removeExternalUserId");
+  }
+
   // Private function that gets called by ObjC/Java
   Future<Null> _handleMethod(MethodCall call) async {
     if (call.method == 'OneSignal#handleReceivedNotification' &&