Swift: Text to Speech in any Language

To start with text to speech, the code below is the basic setup.

let utterance = AVSpeechUtterance(string: "Some text")
utterance.voice = AVSpeechSynthesisVoice(language: "en") //any language that you prefer
let synth = AVSpeechSynthesizer()
synth.speak(utterance)

However, this code requires us to specify the language of the text in the code. To make it more dynamic by allowing it to speak any text by automatically detecting the language, we can use NSLinguisticTagger.dominantLanguage(for: text) to detect the language of the text.

if let language = NSLinguisticTagger.dominantLanguage(for: text) {

    //we now know the language of the text 

    let utterance = AVSpeechUtterance(string: text)
    utterance.voice = AVSpeechSynthesisVoice(language: language) //use the detected language

    let synth = AVSpeechSynthesizer()
    synth.speak(utterance)
} else {
    print("Unknown language")
}

Additionally, we can also control the speed of the speech as well as the pitch/frequency of the speech:

private func readText(_ text:String){
    if let language = NSLinguisticTagger.dominantLanguage(for: text) {
        let utterance = AVSpeechUtterance(string: text)
        utterance.voice = AVSpeechSynthesisVoice(language: language)

        //control speed and pitch
        utterance.pitchMultiplier = 1
        utterance.rate = 0.2

        let synth = AVSpeechSynthesizer()
        synth.speak(utterance)

    } else {
        print("Unknown language")
    }
}