Swift 2 - Method not being called through delegate - ios

Question

Hello learning swift and am stuck with calling a method through delegate. Checked multiple answers with similar issues and have tried the solutions but have not been able to successfully apply them to my own situation however I am close.
I have a delegator class named ViewController that holds a variable I would like to change. I have another view called MoodScroll which serves as the delegate. Moodscroll has a button being used to change the value for the variable in ViewController.
ViewController :
class ViewController: UIViewController, AVAudioPlayerDelegate, MoodScrollDelegate {
var alarmSoundType: String?
func acceptData(data: String?) {
alarmSoundType = "\(data)"
print(data)
}
}
MoodScroll :
protocol MoodScrollDelegate {
func acceptData(data: String?)
}
import UIKit
class MoodScroll: UIViewController {
#IBAction func WTF(sender: AnyObject) {
self.delegate?.acceptData("hello")
print("function called")
}
}
The IBAction calls fine as it prints "function called" in the console however it doesn't pass the value to ViewController as alarmSoundType remains nil and also the print command is not called in ViewController as well.

Answer 1

It seems you still have some confusion about delegation : if ViewController conforms to MoodScrollDelegate protocol, then your ViewController object will be the delegate, not the MoodScroll object.
Where do you set the delegate property of your MoodScroll object ?
If this object is created programmatically from your ViewController object, you should set it after initialization :
myMoodScrollObject.delegate = self
Is the object is created using Interface Builder, you can either use an outlet variable for delegate, or set it in prepareForSegue:sender of your ViewController class :
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let scroll = segue.destinationViewController as? MoodScroll{
scroll.delegate = self
}
}

Answer 2

One picky note: the way you have described your problem, it's actually ViewController what you should call the delegate of MoodScroll. Most likely you're probably forgetting to set the delegate property of MoodScroll.
I don't know how these two view controllers relate to each other in your code, but very often you would set the delegate property in the prepareForSegue method of ViewController, for example:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "SegueToMoodScroll" {
let moodScrollController = segue.destinationViewController as! MoodScroll
moodScrollController.delegate = self
}
}