How to implement a delegate

1. We have the class RecordSoundsViewController of type UIViewController. We want that this class implements a function included inside the class AVAudioRecorderDelegate called audioRecorderDidFinishRecording. The initial class is

class RecordSoundsViewController: UIViewController {

   var audioRecorder:AVAudioRecorder!

   @IBAction func recordAudio(sender: UIButton) {

        ...

        try! audioRecorder = AVAudioRecorder(URL: filePath!, settings: [:])

        ...

    }

}

2. We add the type AVAudioRecorderDelegate to this class

class RecordSoundsViewController: UIViewController, AVAudioRecorderDelegate {

   var audioRecorder:AVAudioRecorder!

   @IBAction func recordAudio(sender: UIButton) {

        ...

        try! audioRecorder = AVAudioRecorder(URL: filePath!, settings: [:])

        ...

    }

}

3. After initialize the audioRecorder instance we declare that the class RecordSoundsViewController will be the delegate for audioRecorder

class RecordSoundsViewController: UIViewController, AVAudioRecorderDelegate {

   var audioRecorder:AVAudioRecorder!

   @IBAction func recordAudio(sender: UIButton) {

        ...

        try! audioRecorder = AVAudioRecorder(URL: filePath!, settings: [:])

        audioRecorder.delegate = self

        ...

    }

}

4. We add a function audioRecorderDidFinishRecording in the class RecordSoundsViewController

class RecordSoundsViewController: UIViewController, AVAudioRecorderDelegate {

   var audioRecorder:AVAudioRecorder!

   @IBAction func recordAudio(sender: UIButton) {

        ...

        try! audioRecorder = AVAudioRecorder(URL: filePath!, settings: [:])

        audioRecorder.delegate = self

        ...

    }

    func audioRecorderDidFinishRecording(recorder: AVAudioRecorder, successfully flag: Bool) {

        <#code#>

    }

}

Concepts:

- Class AVAudioRecorder has a variable called delegate of type AVAudioRecorderDelegate

class AVAudioRecorder{

   var delegate: AVAudioRecorderDelegate!

}

- AVAudioRecorderDelegate is a list of methods, one of them audioRecorderDidFinishRecording

protocol AVAudioRecorderDelegate {

   func audioRecorderDidFinishRecording()

}

- In the RecordSoundsViewController of type AVAudioRecorderDelegate, when we see 

audioRecorder.delegate = self

we say that RecordSoundsViewController is becoming AVAudioRecorder.delegate so RecordSoundsViewController can implement the functions inside AVAudioRecorderDelegate like audioRecorderDidFinishRecording