Not able fetch and display particular data - react native

Question

      import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  Navigator,
  TouchableOpacity,
  Image,
  TextInput,                                            
  TouchableHighlight,                                            
  Alert
} from 'react-native';

import Button from 'react-native-button'
import {Actions} from 'react-native-router-flux'
import Home from './Home'

export class Weight extends Component{
    constructor(props) {
  super(props);

  this.state = {
    data: '',
    data1:'',
    textinput:'',
    entryDate: '',
    systol:''
  }

  componentDidMount(){
    this._onPressButtonGET();
  } 
 _onPressButtonPOST(){
            fetch("url", {
                method: "POST",
                 headers: {
                     'Accept': 'application/json',
                     'Content-Type': 'application/json',
                 },
                body: JSON.stringify({
                    "entryDate":"3/2/2017 2:00 AM",
                    "systol": "120",
                    "mobileType":"ANDROID",
                    "userName":"menutest"

                })})
            .then((response) => response.json())
            .then((responseData) => {
                Alert.alert(
                    "Blood pressure data",
                    "Blood pressure data - " + JSON.stringify(responseData)
                )
            })
            .done();
        }

        _onPressButtonGET ()  {
            fetch("url", {
                method: "POST",
                 headers: {
                     'Accept': 'application/json',
                     'Content-Type': 'application/json',
                 },
                body: JSON.stringify({"mobileType":"ANDROID","userName":"menutest"})})
            .then((response) => response.json())
            .then((responseData) => {
                    this.setState({ data: JSON.stringify(responseData) })
                })

            .done();
        }
    render(){
            return(
                <View>
                    <TouchableHighlight onPress={this._onPressButtonPOST}>
                        <Text>Add</Text> 
                    </TouchableHighlight>


                     <TouchableHighlight onPress={this._onPressButtonGET.bind(this)}>
                        <Text>show</Text>
                       </TouchableHighlight>

                      <Text>{this.state.responseData.entryDate}</Text>
                      <Text>{this.state.responseData.systol}</Text>
                       <Text>hello{this.state.data}</Text> 

                </View>
            );
        }
    }

    module.exports = Weight;

I want to display only systol and entryDate on the screen, but my above code is displaying all the data from web services, How can i edit my code that i want to display only those things? i tried with this.setState({ data: responseData.entryDate }) but this is not working need help. and how to use for loop in _onPressButtonGET() to display all entry dates and systol.

Florin Dobre · Accepted Answer · 2017-03-09 13:08:20Z

1

If response data is an object instead of

this.setState({ data: JSON.stringify(responseData) })

use

this.setState({ entryDate: responseData.entryDate, systol: responseData.systol })

and then in the render use {this.state.entryDate} and {this.state.systol}

First make sure you have a clean code in the constructor (add } after setting the state), then make sure you fetch data from the correct url and not just a string, then make sure you receive the exact data that you need and that is a object, then set the info you need on state as I described above, then use it in the render function.

edited Mar 9, 2017 at 13:08

answered Mar 8, 2017 at 17:54

Florin Dobre

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10 Comments

Prasanna Over a year ago

undefined is not an object (evaluating 'this.state.responsedata.entryData') this is error i am getting.

Florin Dobre Over a year ago

I edited my answer! Make sure you store and update on state only what you need and the keys from the state object are matching the keys used in render.

Florin Dobre Over a year ago

add some console.logs before setting the state like this: console.log(typeof responseData) console.log(Object.keys(responseData)) before this.setState({ entryDate: responseData.entryDate, systol: responseData.systol })

Prasanna Over a year ago

how can i use for loop here? actually i have many entryDate and systol?

Prasanna Over a year ago

console.log() is not making any difference

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