Create your own Siri in Swift | Lil ‘Bits | https://www.youtube.com/watch?v=Sigl3dihEB8

SiriViewController.swift

import UIKit
import Speech

class SiriViewController: UIViewController {

    private static let locale = Locale(identifier: "es-ES")
    private let speechRecognizer = SFSpeechRecognizer(locale: SiriViewController.locale)!
    private var recognitionRequest: SFSpeechAudioBufferRecognitionRequest?
    private var recognitionTask: SFSpeechRecognitionTask?
    private let audioEngine = AVAudioEngine()

    @IBOutlet var label : UILabel!
    @IBOutlet var recordButton : UIButton!

    override public func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        SFSpeechRecognizer.requestAuthorization { status in
            if status == .authorized {
                OperationQueue.main.addOperation {
                    self.recordButtonTapped()
                }
            }
        }
    }

    private func startRecording() throws {
        if let recognitionTask = recognitionTask {
            recognitionTask.cancel()
            self.recognitionTask = nil
        }

        try setAudioSessionCategory(AVAudioSessionCategoryRecord)

        recognitionRequest = SFSpeechAudioBufferRecognitionRequest()

        guard let recognitionRequest = recognitionRequest else {
            return
        }
        recognitionRequest.shouldReportPartialResults = true
        recognitionRequest.taskHint = .dictation
        let inputNode = audioEngine.inputNode
        recognitionTask = speechRecognizer.recognitionTask(with: recognitionRequest) { result, error in
            var isFinal = false
            var transcription = ""
            if let result = result {
                isFinal = result.isFinal
                transcription = result.bestTranscription.formattedString
                self.label.attributedText = self.tag(transcription)
            }
            if error != nil || isFinal {
                self.audioEngine.stop()
                inputNode.removeTap(onBus: 0)

                self.recognitionRequest = nil
                self.recognitionTask = nil

                try? self.read(transcription)

                self.recordButton.setTitle("¡Oye Siri!", for: [])
            }
        }

        let recordingFormat = inputNode.outputFormat(forBus: 0)
        inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer: AVAudioPCMBuffer, when: AVAudioTime) in
            self.recognitionRequest?.append(buffer)
        }

        audioEngine.prepare()
        try audioEngine.start()
        label.text = "Cuéntame..."
    }

    func setAudioSessionCategory(_ category: String) throws {
        let audioSession = AVAudioSession.sharedInstance()
        try audioSession.setCategory(category)
        try audioSession.setMode(AVAudioSessionModeMeasurement)
        try audioSession.setActive(true, with: .notifyOthersOnDeactivation)
    }

    @IBAction func recordButtonTapped() {
        if audioEngine.isRunning {
            audioEngine.stop()
            recognitionRequest?.endAudio()
        } else {
            try? startRecording()
            recordButton.setTitle("¿Que he dicho?", for: [])
        }
    }

    func tag(_ text: String) -> NSAttributedString {
        let tagger = NSLinguisticTagger(tagSchemes: [.lemma, .nameTypeOrLexicalClass], options: 0)
        tagger.string = text

        let range = NSRange(location: 0, length: text.utf16.count)
        var words = [String]()
        var bagOfWords = [String: CGFloat]()
        var lemmas = [String: String]()
        tagger.enumerateTags(in: range, unit: .word, scheme: .lemma, options: []) { tag, tokenRange, _ in
            let word = (text as NSString).substring(with: tokenRange)
            words.append(word)
            lemmas[word] = tag?.rawValue
            if bagOfWords[word] != nil {
                bagOfWords[word]! += 1
            } else {
                bagOfWords[word] = 1
            }
        }
        var colors = [String: UIColor]()
        tagger.enumerateTags(in: range, unit: .word, scheme: .nameTypeOrLexicalClass, options: []) { tag, tokenRange, _ in
            let word = (text as NSString).substring(with: tokenRange)
            colors[word] = tag?.colorValue
        }

        return compose(words, bagOfWords: bagOfWords, lemmas: lemmas, colors: colors)
    }

    private func compose(_ words: [String], bagOfWords: [String: CGFloat], lemmas: [String: String], colors: [String: UIColor]) -> NSAttributedString {
        let result = NSMutableAttributedString()
        words.forEach { word in
            let fontSize = 15 + (bagOfWords[word] ?? 0)
            let attributedWord = NSAttributedString(string: lemmas[word] ?? word,
                                                    attributes: [.foregroundColor : colors[word] ?? .black,
                                                                 .font: UIFont.systemFont(ofSize: fontSize)])
            result.append(attributedWord)
        }
        return result
    }

    func read(_ text: String) throws {
        try setAudioSessionCategory(AVAudioSessionCategoryPlayback)

        let speechUtterance = AVSpeechUtterance(string: text)
        speechUtterance.voice = AVSpeechSynthesisVoice(language: SiriViewController.locale.identifier)
        let speechSynthesizer = AVSpeechSynthesizer()
        speechSynthesizer.speak(speechUtterance)
    }
}

extension NSLinguisticTag {
    public var colorValue: UIColor {
        switch self {
            case .noun: return .red
            case .verb: return .green
            case .adjective: return .blue
            case .adverb: return .cyan
            case .pronoun: return .yellow
            case .determiner: return .magenta
            case .particle: return .gray
            case .preposition: return .darkGray
            case .number: return .lightGray
            case .personalName: return .orange
            case .placeName: return .purple
            case .organizationName: return .brown
            default: return .black
        }
    }
}