Async Storage Error Unhandled Promise Rejection in Switch - react-native

Question

I'm new to react native and now i have a problem.
I'm trying to save my data into local storage using Async Storage, I'm following this tutorial ,
it worked properly but not in my switch code.
This is my constructor
constructor(props) {
super(props)
this.state = {prevBtn: undefined}
this.onPrevValueChange = this.onPrevValueChange.bind(this);
}
then i get the item in my didMount:
componentDidMount() {
this.getQuestionnaire();
AsyncStorage.getItem('prevBtn').then((value) => this.setState({ 'prevBtn': value }));
}
set the value when it change:
onPrevValueChange = (value) => {
AsyncStorage.setItem('prevBtn', value);
this.setState({ prevBtn: value });
}
and render method:
render(){
const {}
return(
<Switch
value={prevBtn}
backgroundActive={'red'}
onValueChange={this.onPrevValueChange}
/>
);
}
Can anybody help please?

Answer 1

issue with setState in componentDidMount, when you setting value for prevBtn using single quotation mark ` so it is behaving like String not a state, use it as below:
componentDidMount() {
this.getQuestionnaire();
AsyncStorage.getItem('prevBtn').then((value) => this.setState({ prevBtn: value }));
}
In render you are using prevBtn directly, use it as this.state.prevBtn.
render(){
const {}
return(
<Switch
value={this.state.prevBtn}
backgroundActive={'red'}
onValueChange={this.onPrevValueChange}
/>
);
}

Answer 2

You need to change your componentDidMount to this:
Note that AsyncStorage.getItem always returns a string, you'll have to convert it to a boolean before using it. And as the other commenter pointed out, you can't have quotes around the state property.
componentDidMount() {
this.getQuestionnaire();
AsyncStorage.getItem('prevBtn').then((value) => {
value === 'true'
? this.setState({ prevBtn: true })
: this.setState({ prevBtn: false })
});
}