this.setState is undefined

Question

I keep seeing answers that say to use => or .bind(this) but neither of those solutions worked.

import React, { Component } from 'react'; import { View, Text, TextInput, StyleSheet } from 'react-native';  export default class MyWeatherApp extends Component {   constructor(props) {   super(props);    this.state = {}; }  getInitialState() {   return {     zip: '',     forecast: null,   }; }  _handleTextChange(event) {   var zip = event.nativeEvent.text;   this.setState({zip: zip}); } 

Solution:

_handleTextChange = (event) => {   var zip = event.nativeEvent.text;   this.setState({zip: zip});   alert('click'); } 

Answer 1

When you extend React.Component with ES2015 class syntax you need to bind your action handlers to a context of your class.

Try this: onChange={e => _handleTextChange(e)}

Generally, it's better not to use arrow functions or bind methods inside render as it generates a new copy of the function on any render call. Move function declaration to the class constructor.

I personally prefer to use arrow functions as class properties in this case

class MyClass extends React.Component {    handleClick = () => {     // your logic   };    render() {     return (       <button onClick={this.handleClick}>Click me</button>     );   } } 

It's not a part of ES2015 specification but babel stage-0 preset supports this syntax

You can read more about context binding in React in this article