Get Data from State React-Native Javascript

Course Queries Syllabus Queries 2 years ago

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Posted on 16 Aug 2022, this text provides information on Syllabus Queries related to Course Queries. Please note that while accuracy is prioritized, the data presented might not be entirely correct or up-to-date. This information is offered for general knowledge and informational purposes only, and should not be considered as a substitute for professional advice.

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manpreet Tuteehub forum best answer Best Answer 2 years ago


This is puzzling me why I can't get data from the state, I have tried many things but not had no luck.

I'm getting data from a firebase database and I am trying to store the data into a state, then I can access that data from the state.

Any suggestions will be appreciated.

Thank you

state = {
   isDateTimePickerVisible: false,
   mode: "time",
   minuteInterval: 30,
   selectedDate: {},
   isLoading: true,
   syllabus: [{value: 'Banana'}],
   users: [{
     value: 'Banana',
     app_id: 'apple',
   }],
  timeSlots:[{
     name: 'test',
     time: '123',
  }],
};

testStore() {

let returnArr = [];

  db.ref('bookings/' + this.user).child("22-09-2018").once('value').then(function(snapshot) {
     let data = snapshot.val();
     let timeSlot = Object.values(data);
     console.log("testStore: " + timeSlot[0].name);
     //gets data from the firebase database -- testStore: james
     dt = timeSlot;

     this.setState({
       timeSlots: dt
     });

}.bind(this));
  this.testState();
}

testState() {
  console.log("test state " + this.state.timeSlots[0].name);
  //Get A red screen with error undefined is not an object(evaluating 'this.state.timeSlots['name']) 
}

    onDayPress(day) {

        console.log("day press " + day.dateString);
        this.testStore();
        var st = day.dateString;
        var dt = new Date(st);

        var today = dt;
        var dd = today.getDate();
        var mm = today.getMonth() + 1; //January is 0!

        var yyyy = today.getFullYear();
        if (dd < 10) {
            dd 
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manpreet 2 years ago

From your complete code, it seems that your constructor is rewriting your state to an empty object (therefore this.state.timeSlots[0].name is indeed problematic)

I'd rewrite your constructor as :

constructor(props) {
    super(props)
    this.state = {
      isDateTimePickerVisible: false,
      mode: 'time',
      minuteInterval: 30,
      selectedDate: {},
      isLoading: true,

      syllabus: [{
        value: 'Banana',
      }],
      users: [{
        value: 'Banana',
        app_id: 'apple',
      }],

      slots: [{
        name: 'test',
        time: '123',
        user_id: '373737',
      }],
    }
this.onDayPress = this.onDayPress.bind(this)
this.testStore = this.testStore.bind(this)

}

and testStore as :

testStore() {
      const returnArr = []

      db.ref(`bookings/${this.user}`).child('22-09-2018').once('value').then((snapshot) => {
        const data = snapshot.val()
        const timeSlot = Object.values(data)

        console.log(`testStore: ${timeSlot[0].name}`)

        dt = timeSlot

        this.setState({
            timeSlots: dt
        }, () => {
            console.log('after setState', this.state.timeSlots)
        })
      })
    }

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