Getting an error after using setState with a promise

Question

Code:

onDragEnd = {     (event) => this.setState({ playerMarkerPositionFuture: event.nativeEvent.coordinate })     .then(() => alert("hello")) } 

When the following code gets executed I receive this error:

undefined is not an object evaluating ('_this.setState({playerMarkerPositionFuture: event.nativeEvent.coordinate}).then') 

If I remove the promise everything works as expected so it means that most likely I used the promise in a wrong way:

onDragEnd={     (event) => this.setState({ playerMarkerPositionFuture: event.nativeEvent.coordinate }) }  

Answer 1

setState accepts a callback, but it doesn't return a promise. See docs

Calls to setState are asynchronous - don’t rely on this.state to reflect the new value immediately after calling setState. Pass an updater function instead of an object if you need to compute values based on the current state (see below for details).

(event) => {     this.setState({playerMarkerPositionFuture: event.nativeEvent.coordinate }, () => alert("hello")); }