SOLVED: Using async await with older asynchronous Swift API's

@davidhughes85

Feb '22

I am currently in the process of converting my app to use aync await, however I have hit a blocker when it comes to using older asynchronous Swift API methods, more specifically the requestRecordPermission on AVAudioSession.

The ideal would be doing something like this:

@MainActor func startCall(sip: SIP, meeting: Meeting) async throws {
    let granted = try await AVAudioSession.sharedInstance().requestRecordPermission()

    if granted {
        // more stuff here...
        let call = try await callAgent?.startCall(participants: [pstnCallee], options: startCallOptions)
        self.call = call
        self.call?.delegate = self
    } else {
        throw SomeError.custom
    }
}

So I have tried to use the old API using withCheckedThrowingContinuation.

func startCall(sip: SIP, meeting: Meeting) async throws {
    return try await withCheckedThrowingContinuation { continutation -> Void in
        AVAudioSession.sharedInstance().requestRecordPermission { [weak self] granted in
            guard let strongSelf = self else {
                continutation.resume(throwing: SomeError.custom)
            }

            if granted {
                // more stuff here

                do {
                    let call = try await strongSelf.callAgent?.startCall(participants: [pstnCallee], options: startCallOptions)
                    strongSelf.call = call
                    strongSelf.call?.delegate = strongSelf
                    continutation.resume(returning: ())
                } catch {
                    continutation.resume(throwing: error)
                }
            }
        }
    }
}

But Xcode is throwing the following error on line 3: Cannot pass function of type '(Bool) async -> Void' to parameter expecting synchronous function type

Any suggestions on how to fix this?

@davidhughes85

Feb '22

I have actually figured it out by extending AVAudioSession.

import AVFoundation

extension AVAudioSession {
    func requestRecordPermission() async -> Bool {
        await withCheckedContinuation { continuation in
            requestRecordPermission { granted in
                continuation.resume(returning: granted)
            }
        }
    }
}

Then at the call site:

func requestMicrophonePermission() async -> Bool {
    await AVAudioSession.sharedInstance().requestRecordPermission()
}

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