session.setPreferredInput in Swift? - ios

Question

I am trying to set the preferred input to my AVAudioEngine. I have the following code:
var iphoneInput: AVAudioSessionPortDescription = AVAudioSession.sharedInstance().availableInputs[0] as! AVAudioSessionPortDescription
var error: NSError?
session.setPreferredInput(inPort: iphoneInput, error: error)
but Xcode keeps giving me errors for the last line stating taht it cannot invoke setPreferredinput with an arguement list of type '(AVAudioSessionPortDescription, NSError?)'
I am assuming it wants a NSErrorPointer for the error but I do not know how to create one in swift. Is this my problem and if so how do I create one? thanks!

Answer 1

Add a & character before the variable to make it a pointer:
var myError: NSError?
session.setPreferredInput(iphoneInput, error: &myError)
if myError == nil {
// do stuff
}
Note: in Swift you don't have to use the method's first parameter's name.

Answer 2

for swift 3 does not work... you have to do (translated from ADC:
https://developer.apple.com/library/content/qa/qa1799/_index.html
)
private func setupSession(){
let session = AVAudioSession.sharedInstance()
// setup session:
do {
try session.setCategory(AVAudioSessionCategoryPlayAndRecord, with: .defaultToSpeaker)
try session.setActive(true)
}
catch _{
}
// https://developer.apple.com/library/content/qa/qa1799/_index.html
// let portDescr = AVAudioSessionPortDescription()
// headers:
// AVAudioSessionPortLineIn: String // Line level input on a dock connector
// AVAudioSessionPortBuiltInMic: String // Built-in microphone on an iOS device
// AVAudioSessionPortHeadsetMic: String // Microphone on a wired headset. Headset refers to an accessory that has headphone outputs paired with a microphone.
// You cannot set directly..
// portDescr.portType = AVAudioSessionPortLineIn
guard let availableInputs = session.availableInputs else {
return
}
var mic : AVAudioSessionPortDescription? = nil
for input in availableInputs {
if input.portType == AVAudioSessionPortBuiltInMic{
mic = input
}
}
guard mic != nil else{
return
}
do {
try session.setPreferredInput(mic)
}catch _ {
print("cannot set mic ")
}
}