Amazon Alexa - Undefined speech response

Question

I am trying to invoke the "AskQuestion" in the "SetLanguageIntent" to construct a speech to the user, using Alexa fact skill blueprint.

'SetMyLanguageIntent': function() {
    this.attributes['language'] = this.event.request.intent.slots.languages.value;
    var language = this.attributes['language'];

    this.response
      .speak('Okay, I will ask you some questions about ' +
        language + '. Here is your first question.' +
        this.AskQuestion).listen(this.AskQuestion);
    this.emit(':responseReady');
  },

'AskQuestion': function() {
    var language = this.attributes['language'];
    var currentQuestion = flashcardsDictionary[this.attributes['currentFlashcardIndex']].question;

    return 'In ' + language + ', ' + currentQuestion;
  },

This is the server's response:

{
  "version": "1.0",
  "response": {
    "outputSpeech": {
      "ssml": "<speak> Okay, I will ask you some questions about undefined. Here is your first question.undefined </speak>",
      "type": "SSML"
    },
    "reprompt": {
      "outputSpeech": {
        "ssml": "<speak> undefined </speak>",
        "type": "SSML"
      }
    },

Alexa utters the word "undefined" in the response, Here is the dialogue: "Okay, I will ask you some questions about undefined. Here is your first question. undefined"

Why is the response "undefined"? and how to go about fixing this issue?

Here is the the whole Code:

'use strict';

var Alexa = require('alexa-sdk');

var flashcardsDictionary = [{
    question: 'how do you find the length of a string?',
    rubyAnswer: 'length',
    pythonAnswer: 'Len',
    javascriptAnswer: 'length'
  },
  {
    question: 'how do you print to the console or terminal?',
    rubyAnswer: 'puts',
    pythonAnswer: 'print',
    javascriptAnswer: 'console.log'
  },
  {
    question: 'are boolean terms capitalized or not capitalized?',
    rubyAnswer: 'not capitalized',
    pythonAnswer: 'capitalized',
    javascriptAnswer: 'not capitalized'
  }
];

var DECK_LENGTH = flashcardsDictionary.length;

var handlers = {
  // Open Codecademy Flashcards
  'LaunchRequest': function() {
    this.attributes['language'] = '';
    this.attributes['numberCorrect'] = 0;
    this.attributes['currentFlashcardIndex'] = 0;

    this.response
      .listen('Welcome to Flashcards. In this session, do you want to test' +
        ' your knowledge in Ruby, Python, or Javascript?').speak(
        'Which language would you like to practice?');
    this.emit(':responseReady');
  },

  'SetMyLanguageIntent': function() {
    this.attributes['language'] = this.event.request.intent.slots.languages.value;
    var language = this.attributes['language'];

    this.response
      .speak('Okay, I will ask you some questions about ' +
        language + '. Here is your first question.' +
        this.AskQuestion).listen(this.AskQuestion);
    this.emit(':responseReady');
  },

  // User gives an answer
  'AnswerIntent': function() {
    var userAnswer = this.event.request.intent.slots.answer.value;
    var language = this.attributes['language'];
    var languageAnswer = language + userAnswer;
    var correctAnswer = flashcardsDictionary[this.attributes['currentFlashcardIndex']][languageAnswer];


    if (userAnswer === correctAnswer) {
      this.attributes['numberCorrect']++;
      var numberCorrect = this.attributes['numberCorrect'];

      this.response
        .speak('Nice job! The correct answer is ' + correctAnswer + '. You ' +
          'have gotten ' + numberCorrect + ' out of ' + DECK_LENGTH + ' ' +
          language + ' questions correct.' + this.AskQuestion)
        .listen(this.AskQuestion);


    } else {
      var numberCorrect = this.attributes['numberCorrect'];

      this.response
        .speak('Sorry, the correct answer is ' + correctAnswer + '. You ' +
          'have gotten ' + numberCorrect + ' out of ' + DECK_LENGTH + ' ' +
          language + ' questions correct. Here is your next question.' +
          this.AskQuestion).listen(this.AskQuestion);
    }

    this.attributes['currentFlashcardIndex']++;

    this.emit(':responseReady');
  },

  // Test my {language} knowledge
  'AskQuestion': function() {
    var language = this.attributes['language'];
    var currentQuestion = flashcardsDictionary[this.attributes['currentFlashcardIndex']].question;

    return 'In ' + language + ', ' + currentQuestion;
  },

  // Stop
  'AMAZON.StopIntent': function() {
    this.response.speak('Ok, let\'s play again soon.');
    this.emit(':responseReady');
  },

  // Cancel
  'AMAZON.CancelIntent': function() {
    this.response.speak('Ok, let\'s play again soon.');
    this.emit(':responseReady');
  }
};

exports.handler = function(event, context, callback) {
  var alexa = Alexa.handler(event, context);
  alexa.registerHandlers(handlers);
  alexa.execute();
};

Answer 1

请使用this.AskQuestion()代替this.AskQuestion因为AskQuestion是函数而不是对象。