如何使用mapStateToProps将数据从Redux状态获取到组件中

Question

我正在尝试使用mapstatetoprops将数据传递到组件中。问题是数据是从后端提取到减速器中的，但是在我的组件中，我得到了一个空的Array []，随后出现未定义的错误

当我从后端断开连接并将数据放置在reducer内时，一切正常，但是一旦我重新连接到Redux，数据就不会超出Reducer（我正在使用MERN堆栈）

My Reducer

const initialState = {
    quizes : [ ]
    loading: false

}

export default function(state=initialState,action){

    switch(action.type){
           case GET_QUIZ:

               //The result of the
                  log below successfully gives
                   me back data fetched from the API/backend//

               console.log(action.payload)
                  return{
                         ...state,
                         quizes:action.payload,
                         loading:false

                  }

                  case QUIZ_LOADING:
                      return{
                          ...state,
                          loading:true
                      }
                  default:
                         return state;
    }
}




.................................................................
my App


class QuestionApp extends Component {
 constructor(props) {
    super(props);

    this.state = {

      counter: 0,
      questionId: 1,
      question: '',
      answerOptions: [],
      answer: '',
      answersCount: {
        Smart: 0,
        Subpar: 0,
        Confused: 0
      },
      result: ''
    };

    this.handleAnswerSelected = this.handleAnswerSelected.bind(this);

  }


componentDidMount() {
    this.props.getQuiz();
//The result of the log beow gives me back an empty Array//

    console.log(this.props.quiz.quizes)
    const shuffledAnswerOptions = this.props.quiz.quizes.map((question) =>
     this.shuffleArray(question.answers));
    this.setState({

// the error appears on next line : Uncaught TypeError: Cannot read property 'question' of undefined

      question: this.props.quiz.quizes[0].question,
      answerOptions: shuffledAnswerOptions[0]
        });
  }

//Remaining body of code


QuestionApp.propTypes ={
  getQuiz:PropTypes.func.isRequired,
  quiz:PropTypes.object.isRequired
}
const mapStateToprops=(state)=>({
quiz: state.quiz
});

export default connect(mapStateToprops,
  {getQuiz})(QuestionApp)

...................................................................

CombineReducer 

export default combineReducers({

    quiz:quizReducer,
    user: userReducer

});

sample of the Data = quizes:[]

[
    {
        question: "What is 4 X 4 ? ",
        answers: [
            { type: "Smart",content: "16" },



            {
                type: "Subpar",
                content: "15"
            },
            {
                type: "Confused",
                content: "1"
            }
        ]

    },

.......................................................................
My Schema
const QuizSchema = new Schema({

    question: {
        type:String,
        default:''
    },
    answers: [{
        type: {
            type: String,
            default:''
        },
        content: {
            type: String,
            default:''
        },
    }]
});

module.exports=Quiz=mongoose.model('quizes',QuizSchema,'quiz');