AVSpeechSynthesizerDelegate implementation in SwiftUI - swiftui

Question

Can anyone share how we can implement AVSpeechSynthesizerDelegate in SwiftUI.
how we can listen to delegate callbacks methods in SwiftUI app.
Thanks

Answer 1

One solution would be to define a class which conforms to ObservableObject. The idea would be to use an #Published property to enable SwiftUI to make updates to your UI. Here's an example of a simple way to keep track of the state of an AVSpeechSynthesizer (I'm unsure of your actual use case):
final class Speaker: NSObject, ObservableObject {
#Published var state: State = .inactive
enum State: String {
case inactive, speaking, paused
}
override init() {
super.init()
synth.delegate = self
}
func speak(words: String) {
synth.speak(.init(string: words))
}
private let synth: AVSpeechSynthesizer = .init()
}
Then, make this class conform to AVSpeechSynthesizerDelegate like so:
extension Speaker: AVSpeechSynthesizerDelegate {
func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didStart utterance: AVSpeechUtterance) {
self.state = .speaking
}
func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didPause utterance: AVSpeechUtterance) {
self.state = .paused
}
func speechSynthesizer(_ synthesizer: AVSpeechSynthesizer, didFinish utterance: AVSpeechUtterance) {
self.state = .inactive
}
// etc...
}
Here, I've simply used the delegate callbacks to update a single #Published property, but you could update however you like here depending on your use case. The main point to bear in mind with ObservableObjects is using the #Published property wrapper for any properties you wish to drive UI updates upon a change in value. Here's an example view:
struct MyView: View {
#ObservedObject var speaker: Speaker
var body: some View {
// 1
Text("State = \(speaker.state.rawValue)")
.onReceive(speaker.$state) { state in
// 2
}
}
}
Note how there's two ways to use #Published properties in SwiftUI Views. 1: Simply read the value. SwiftUI will update your view upon a value change. 2: Access the #Published property's publisher with the $ prefix. Using Views onReceive method, you can execute code whenever the publisher emits a value.