applyDerivedStateFromProps() — react Function Reference

Source Code

packages/react-reconciler/src/ReactFiberClassComponent.js lines 129–163

function applyDerivedStateFromProps(
  workInProgress: Fiber,
  ctor: any,
  getDerivedStateFromProps: (props: any, state: any) => any,
  nextProps: any,
) {
  const prevState = workInProgress.memoizedState;
  let partialState = getDerivedStateFromProps(nextProps, prevState);
  if (__DEV__) {
    if (workInProgress.mode & StrictLegacyMode) {
      setIsStrictModeForDevtools(true);
      try {
        // Invoke the function an extra time to help detect side-effects.
        partialState = getDerivedStateFromProps(nextProps, prevState);
      } finally {
        setIsStrictModeForDevtools(false);
      }
    }
    warnOnUndefinedDerivedState(ctor, partialState);
  }
  // Merge the partial state and the previous state.
  const memoizedState =
    partialState === null || partialState === undefined
      ? prevState
      : assign({}, prevState, partialState);
  workInProgress.memoizedState = memoizedState;

  // Once the update queue is empty, persist the derived state onto the
  // base state.
  if (workInProgress.lanes === NoLanes) {
    // Queue is always non-null for classes
    const updateQueue: UpdateQueue<any> = (workInProgress.updateQueue: any);
    updateQueue.baseState = memoizedState;
  }
}