How to change state value in react native? - react-native

Question

I have problem in changing value of state.It gives mi following error
"Undefine is not a function(evaluating '
this.setState({
switchValue:false
})')"
I have search on stack overflow but the solution is not work for me.
import React, { Component } from 'react';
import {
Alert,
AppRegistry,
StyleSheet,
Text,
View,
Switch
} from 'react-native';
export default class AwesomeProject extends Component {
constructor(props) {
super(props);
this.state = {switchValue: true};
// Toggle the state every second
}
_onPressButton() {
this.setState({
switchValue: false
});
}
render() {
return (
<View style={styles.container}>
<Text style={styles.welcome}>
Welcome to React Native!
</Text>
<Switch
onValueChange={this._onPressButton}
value={this.state.switchValue }
/>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
},
welcome: {
fontSize: 20,
textAlign: 'center',
margin: 10,
},
instructions: {
textAlign: 'center',
color: '#333333',
marginBottom: 5,
},
});
AppRegistry.registerComponent('AwesomeProject', () => AwesomeProject);

Answer 1

The this inside _onPressButton is not referencing the correct reference. On that case, this inside that _onPressButton is actually reference the button. You can either do this two ways.
<Switch
onValueChange={this._onPressButton.bind(this)}
value={this.state.switchValue }
/>
Or
<Switch
onValueChange={() => this._onPressButton()}
value={this.state.switchValue }
/>