Making a non-instantaneous change with an #IBAction button in Swift - ios

Question

I am trying to change the value of the speech rate property of my AVSpeechUtterance upon clicking a button in my app. I then want this value to carry over when I press the "speak" button.
If that explanation wasn't clear enough imagine this:
There are three buttons: one, two and three.
When the user presses one, the value of a the rate of an utterance changes (The same goes for the two and three).
Then after pushing one of the first three buttons, the user pushes another button that activates an utterance. This utterance will carry over the rate value and apply it to the speech.
Here is the code I have tried but doesn't work:
import UIKit
import AVFoundation
class SecondViewController: UIViewController {
#IBOutlet var minutesLabel: UITextField!
#IBOutlet var secondsField: UITextField!
func speak(sender: AnyObject) {
let speechUtterance = AVSpeechUtterance(string:exampleSpeech)
speechSynthesizer.speakUtterance(speechUtterance)
}
#IBOutlet var result: UILabel!
#IBAction func verySlow(sender: UIButton) {
let verySlowButtonPressed = true
let talkingSpeed = 90
let minutesValue : Double = (minutesLabel.text as NSString!).doubleValue
let secondsValue = (secondsField.text as NSString!).doubleValue
let secondsToMinutes = secondsValue / 60
let compiledTime = Double(minutesValue) + Double(secondsToMinutes)
let resultingWords = Double(compiledTime) * Double(talkingSpeed)
let resultCeiling = ceil(resultingWords)
result.text = "\(String(format: "%.0f", resultCeiling)) words"
if verySlowButtonPressed {
speechUtterance.rate = 0.25
speechUtterance.pitchMultiplier = 0.25
speechUtterance.volume = 0.75
}
}
#IBAction func speakButton(sender: AnyObject) {
speak(exampleSpeech)
}

Answer 1

In your speak function you are creating a new AVSpeechUtterance instance every time it's called. When your verySlow function is called, it's setting the rate, pitchMultiplier, and volume on what I'm presuming is a class property called speechUtterance. Since you're creating a new AVSpeechUtterance in speak each time it's called, those properties that you are setting in verySlow are not going to be set on the same instance.
One way to solve this would be to make rate, pitchMultiplier, and volume properties in your class, set those in your verySlow function, and then set them on speechUtterance after you create it in your speak function.
Something like:
var rate: Float?
var pitchMultiplier: Float?
var volume: Float?
func speak(sender: AnyObject) {
let speechUtterance = AVSpeechUtterance(string:exampleSpeech)
if let rate = self.rate {
speechUtterance.rate = rate
}
if let pitchMultiplier = self.pitchMultiplier {
speechUtterance.pitchMultiplier = pitchMultiplier
}
if let volume = self.volume {
speechUtterance.volume = volume
}
speechSynthesizer.speakUtterance(speechUtterance)
}
#IBAction func verySlow(sender: UIButton) {
// ... whatever other code you need here ...
self.rate = 0.25
self.pitchMultiplier = 0.25
self.volume = 0.75
}

Answer 2

Not sure but these are the value for speech rate, try using them. I hope it helps.
iOS 9
Very Slow -- 0.42
Slower -- 0.5
My Normal -- 0.53
Faster -- 0.56
Value are different for previous versions of iOS, please keep that in mind while implementing the solution.