Ios 同时使用AVSpeechSynthesizer的两个实例

我想同时使用两个AVSpeechSynthesizer实例

let firstSynthesizer = AVSpeechSynthesizer()
let secondSynthesizer = AVSpeechSynthesizer()

func foo() {
   let utterance = AVSpeechUtterance(string: "Foo Foo Foo Foo Foo")
   utterance.rate = 0.4
   utterance.voice = AVSpeechSynthesisVoice(language: "en-US")
   firstSynthesizer.speak(utterance)
}

func bar() {
   let utterance = AVSpeechUtterance(string: "Bar Bar Bar Bar Bar")
   utterance.rate = 0.4
   utterance.voice = AVSpeechSynthesisVoice(language: "en-US")
   secondSynthesizer.speak(utterance)
}

当我调用

foo（）

和

bar（）

时，文本不会同时读取，而是一个接一个地读取

我想同时使用两个AVSpeechSynthesizer实例

let firstSynthesizer = AVSpeechSynthesizer()
let secondSynthesizer = AVSpeechSynthesizer()

func foo() {
   let utterance = AVSpeechUtterance(string: "Foo Foo Foo Foo Foo")
   utterance.rate = 0.4
   utterance.voice = AVSpeechSynthesisVoice(language: "en-US")
   firstSynthesizer.speak(utterance)
}

func bar() {
   let utterance = AVSpeechUtterance(string: "Bar Bar Bar Bar Bar")
   utterance.rate = 0.4
   utterance.voice = AVSpeechSynthesisVoice(language: "en-US")
   secondSynthesizer.speak(utterance)
}

这在iOS 12中绝对不可能，一次只能对一个语音合成进行语音处理

不过，可以和语音合成一起播放