Call Flutter from native iOS and get value back using Pigeon FlutterApi

Question

I'm using Pigeon library to connect Flutter and native platform code, in particular iOS with Swift.

I want to call a flutter function from Swift and get a value back, all synchronously.

The function on flutter is defined like this:

@FlutterApi()
abstract class MyFlutterApi {
    String? didSyncFunctionCalled();
}

Here the Swift code:

let flutterApi: MyFlutterApi?

public func callSyncFunction() -> String? {
    flutterApi?.didSyncFunctionCalled(completion: { (value: String?, error: Error?) in
        return value
    })
}

As you can see the function returns a string (nullable) and I need that string from flutter.

This implementation is incorrect. I get an error from XCode on the line of return value -> Cannot convert value of type 'String?' to closure result type 'Void'

From what I understood, Pigeon always generates code with completion closure with error and eventually a value to return.

This is the solution I don't want to use:

public func callSyncFunction(completion: @escaping (String?) -> Void) {
    flutterApi?.didSyncFunctionCalled(completion: { (value: String?, error: Error?) in
        completion(value)
    })
}

Is there a method to define functions that can be used like this in native code?

public func callSyncFunction() -> String? {
    let value: String? = flutterApi?.didSyncFunctionCalled()
    return value
}

Answer 1

You only return data synchronously the requests from the API is async. It is all built on MethodChannels so the async functionality did not dissapear its more of wrapped up.