Passing custom object through method channel flutter

Question

I am trying to pass a custom object which is of type User from native platform to Flutter. The User class is part of a library and not accessible directly for editing. Here is my android and iOS code implementation for the same. Problem is I am not able to find a solution on how to pass this object through method channels in such a way that I can parse it in the Dart code easily.

Android part:

private fun loginUser(uid: String, apiKey: String, result: MethodChannel.Result) {
        MyChat.login(uid, apiKey, object : MyChat.CallbackListener<User>() {
            override fun onSuccess(user: User) {
                Log.e(TAG, user.toString())
                result.success(hashMapOf("RESULT" to true, "AVATAR" to user.avatar,
                        "CREDITS" to user.credits,
                        "EMAIL" to user.email,
                        "LAST_ACTIVE" to user.lastActiveAt,
                        "NAME" to user.name,
                        "ROLE" to user.role,
                        "STATUS" to user.status,
                        "STATUS_MESSAGE" to user.statusMessage).toString())
            }

            override fun onError(p0: MyChatException?) {
                Log.e(TAG, p0?.message)
                result.error("FAILED", "Unable to create login", null)
            }
        })
    } 

iOS implementation:

func loginUser(result: @escaping FlutterResult, uid: String, apiKey: String){
        MyChat.login(UID: uid, apiKey: apiKey, onSuccess: { (user) in
            // Login Successful
            let data: [String: Any] = ["RESULT":true,
                                       "AVATAR":user.avatar!,
                                       "CREDITS": user.credits,
                                       "EMAIL": user.email!,
                                       "LAST_ACTIVE":String(user.lastActiveAt),
                                       "NAME":user.name!,
                                       "ROLE":user.role!,
                                       "STATUS":user.status.rawValue,
                                       "STATUS_MESSAGE":user.statusMessage]
            let jsonData =  try? JSONSerialization.data(withJSONObject: data, options: [.prettyPrinted])
            result(String(data: jsonData!, encoding: .ascii))
        }) { (error) in
            // Login error
            result(FlutterError(code: "FAILED", message:"Login failed with exception: " + error.errorDescription, details: nil))

        }
    }

My dart code:

    Future<String> isUserLoggedIn() async {
    String status = "";
    try {
      final String result = await platform
          .invokeMethod('loginUser', {"UID": UID, "API_KEY": API_KEY});
      print(result); //How to parse?
    status = "Hello";
    } on PlatformException catch (e) {
      print("Exception");
      status = e.message;
    }
    return status;
  }

Solution 1

You can pass data in hash map.

In Android:

result.success(hashMapOf(
    "CREDITS" to user.credits,
    "EMAIL" to user.email,
    ...
))

In iOS:

let data: [String: Any] = [...]
result(data)

In Flutter:

final result = await platform.invokeMethod<Map<String, dynamic>>('loginUser', ...);
final credits = result['CREDITS'] as String;
final email = result['EMAIL'] as String;
...

Solution 2

you can use invokeMapMethod which is an implementation of invokeMethod that can return typed maps. like this :

final result = await platform.invokeMapMethod('loginUser', ...);

or you can pass json object as string like that :

in android

platform.success(
    "{\"CREDITS\":\"${user.credits}\",\"EMAIL\":\"${user.email}\",\"LAST_ACTIVE\":\"${user.lastActiveAt}\"}"
)

in flutter

var result = await methodChannel.invokeMethod('loginUser' , '');
var json = json.decode(result);

var credit = json['CREDITS'];
var email = json['EMAIL'];
var lastActive = json['LAST_ACTIVE'];

Comments

[Zufar Muhamadeev]

Does it mean we can't return custom objects?

[Vinoth Vino]

I need to send a file object from the flutter app to the iOS native app, I can get the value as dictionary after that which type I need to downcast from any object in swift?

[Pavel]

@Vinoth consider passing path to file as String

[Vinoth Vino]

Yeah thanks, @Pavel. Currently, I'm sending the file path only. But we can also send bytes to native iOS and in the appdelegate, we can get it like let data: FlutterStandardTypedData = call.arguments as! FlutterStandardTypedData