您可以尝试使用SFSpeechAudioBufferRecognitionRequest的contextualStrings属性设置高优先级或设置词汇表中没有的某些单词。有关详细信息，请查看此处：https://developer.apple.com/documentation/speech/sfspeechrecognitionrequest/1649391-contextualstrings?language=objc

SFSpeechAudioBufferRecognitionRequest *recognitionRequest = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
    recognitionRequest.contextualStrings = @[@"Your specific word", @"short custom phrases that are unique to your app"];

我认为你不能限制SFSpeechRecognizer的词汇量，但只有当你想要的单词被识别时，你才能发射action。
当你得到你的输出，你可以尝试这样做：

self.recognitionTask = speechRecognizer?.recognitionTask(with: recognitionRequest, resultHandler: { (result, error) in
    if result == "Desired word one" {
        // Do something
    } else if result == "Desired word two" {
        // Do something else
    } else {
        // Don't do anything
    }
})

经过反复试验，最好的解决方案是将桑塔塔姆和加拉西诺的答案结合起来。
您可以首先通过设置contextualStrings ...来指定所有应该“优先化”的命令。

var contextualString = ["hello world", "goodbye world"]
recognitionRequest.contextualStrings = contextualString

...然后在recognitionTask中过滤这些结果：

recognitionTask = speechRecognizer.recognitionTask(with: recognitionRequest) { result, error in
    var isFinal = false
    
    if let result = result {                
        for transcription in result.transcriptions {
            print("Pondering \(result.bestTranscription.formattedString)")
            if contextualString.contains(transcription.formattedString.lowercased()) {
                print("Found \(transcription.formattedString)")
            }
        }
    }
    
    //...
}

如果您想尝试使用它并测试其限制，可以在https://developer.apple.com/documentation/speech/recognizing_speech_in_live_audio中找到示例代码