This error usually happens when you call the React setState method in a Class component's constructor.
The reason is that the component state is not yet initialized when the constructor is called.
This code will cause the warning Can't call setState on a component that is not yet mounted because it tries
to access the setState method in the component state that is not initialized yet.
constructor(){
super(props)
//this.state is undefined at this point
this.setState({hasError : false})
}To fix the warning, initialize the state in the Class constructor.
constructor(){
super(props)
//initialize the state with the variable
this.state = ({hasError : false})
}
This warning can also happen if you call a method from the Class constructor that sets the state using setState.
constructor(){
super(props)
this.callApi("api_url")
}
callApi(url: string){
//This statement is called from the constructor. Therefore, the
//component state is not yet initialized
this.setState({didReceiveResponse: false})
}
Use componentDidMount or componentWillMount lifecycle methods to call any methods that set the state using setState.
constructor(){
super(props)
//Move this method in to componentDidMount or componentWillMount
//this.callApi("api_url")
}
componentWillUnmount(){
this.callApi("api_url")
}
callApi(url: string){
this.setState({didReceiveResponse: false})
}
