static getDerivedStateFromError()

Question

I was reading a doc about Error boundaries. In that how did static getDerivedStateFromError() lifecycle update the state of hasError without setState?

  class ErrorBoundary extends React.Component {
  constructor(props) {
    super(props);
    this.state = { hasError: false };
  }

  static getDerivedStateFromError(error) {
    return { hasError: true };
  }

  render() {
    if (this.state.hasError) {
      return <h1>Something went wrong.</h1>;
    }

    return this.props.children; 
  }
}

Answer 1

It is just a React internals.

React is responsible for the execution of lifecycle methods (as well as render). If so, React can wrap such methods into try/catch to handle errors by the execution of the getDerivedStateFromError method and consequent setState.

static nature of this method is needed to exclude the possibility of any side-effects on component.