How to use passed parameters in swift setMethodCallHandler - self?.methodName(result: result)

Question

I'm trying to send arguments in an onPressed function in Flutter through a method channel to Swift, and pass those arguments as parameters to the Swift method that is called.

I've been tasked with creating a Flutter UI that calls on controllers written in Swift. I've seen examples here that utilize arguments sent with the platform.invokeMethod in Flutter, but they don't use those arguments in a method call inside the setMethodCallHandler method on the Swift side. I can't figure out how to include those arguments in the method I want to invoke if the call.method matches what I sent through.

1.The button widget in main.dart:

    RaisedButton(
          child: Text('Get a Number'),
          onPressed: () => _getNumber(6, 2),
        )

2. The async Flutter function in main.dart:

    Future<void> _getNumber(int number, int times) async {
String numberText;
try {
  final int result = await platform.invokeMethod('multiply', <String, dynamic>{
    "number": number,
    "times": times
  });
  numberText = "Your number is $result .";
} on PlatformException catch (e) {
  numberText = "Failed to get a number: '${e.message}'.";
}

setState(() {
  _numberText = numberText;
});}

3. My method call handler in appDelegate.swift:

    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
    let customChannel = FlutterMethodChannel(name: "samples.flutter.dev",
                                            binaryMessenger: controller)
    customChannel.setMethodCallHandler({
    [weak self] (call: FlutterMethodCall, result: FlutterResult) -> Void in

    switch call.method {
      case "getBatteryLevel":
        self?.receiveBatteryLevel(result: result)
      case "multiply":
        self?.multiply(result: result)
      default:
        result(FlutterMethodNotImplemented)
    }

4. My private function that handles this specific multiplication:

    private func multiply(result: FlutterResult) {
         // here I want to access the "number" and "times"
        // arguments that I passed in from Flutter
      result(Int(number * times))
    }

Since I'm pretty new to swift and dart, I am struggling to figure out how to navigate/utilize the result: FlutterResult. How can I change that parameter or access its properties to use the number and times arguments I passed into the onPressed function in Flutter?

Answer 1

Change your multiply method to start like this - pass call in:

private func multiply(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
  if let args = call.arguments as? Dictionary<String, Any>,
    let number = args["number"] as? Int,
    let times = args["times"] as? Int {
    // use number and times as required, for example....
    result(number * times) // or your syntax
  } else {
    result(FlutterError.init(code: "bad args", message: nil, details: nil))
  }