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React16源码: React中commitAllHostEffects内部的commitWork源码实现

commitWork


1 ）概述

  • 在 react commit 阶段的 commitRoot 第二个while循环中
  • 调用了 commitAllHostEffects，这个函数不仅仅处理了新增节点，
  • 若一个节点已经存在，当它有新的内容要更新或者是它的attributes要更新
  • 这个时候，就需要调用 commitWork

2 ）源码

定位到 packages/react-reconciler/src/ReactFiberCommitWork.js#L1033

function commitWork(current: Fiber | null, finishedWork: Fiber): void {
  if (!supportsMutation) {
    switch (finishedWork.tag) {
      case FunctionComponent:
      case ForwardRef:
      case MemoComponent:
      case SimpleMemoComponent: {
        commitHookEffectList(UnmountMutation, MountMutation, finishedWork);
        return;
      }
    }

    commitContainer(finishedWork);
    return;
  }

  // 首先，根据不同的tag类型来执行不同的操作
  switch (finishedWork.tag) {
    case FunctionComponent:
    case ForwardRef:
    case MemoComponent:
    case SimpleMemoComponent: {
      commitHookEffectList(UnmountMutation, MountMutation, finishedWork);
      return;
    }
    // ClassComponent 不在这里的执行范围内，所以它就return了
    case ClassComponent: {
      return;
    }
    case HostComponent: {
      const instance: Instance = finishedWork.stateNode;
      // // 如果instance不等于null，就代表 instance 对应的节点已经创建了
      if (instance != null) {
        // Commit the work prepared earlier.
        const newProps = finishedWork.memoizedProps;
        // For hydration we reuse the update path but we treat the oldProps
        // as the newProps. The updatePayload will contain the real change in
        // this case.
        const oldProps = current !== null ? current.memoizedProps : newProps;
        const type = finishedWork.type;
        // TODO: Type the updateQueue to be specific to host components.
        // 获取了一个 updatePayload 等于 finishedWork.updateQueue
        // 在 completeWork 的时候，对于 HostComponent 进行了新老 props 的一个对比
        // 这个对比的结果就是返回一个叫做 updatePayload 这么一个数组
        // 这个数组是以2为单位，就是说一个key一个value, 它的第一位是key，第二位是value，然后这样的形式一个一个往后面堆叠
        // 拿到这么一个 updatePayload 之后，我们就知道在commit阶段要去执行怎么样的一个更新操作
        const updatePayload: null | UpdatePayload = (finishedWork.updateQueue: any);
        finishedWork.updateQueue = null;
        // 存在 updatePayload 则执行 commitUpdate
        if (updatePayload !== null) {
          commitUpdate(
            instance,
            updatePayload,
            type,
            oldProps,
            newProps,
            finishedWork,
          );
        }
      }
      return;
    }
    case HostText: {
      invariant(
        finishedWork.stateNode !== null,
        'This should have a text node initialized. This error is likely ' +
          'caused by a bug in React. Please file an issue.',
      );
      const textInstance: TextInstance = finishedWork.stateNode;
      const newText: string = finishedWork.memoizedProps;
      // For hydration we reuse the update path but we treat the oldProps
      // as the newProps. The updatePayload will contain the real change in
      // this case.
      const oldText: string =
        current !== null ? current.memoizedProps : newText;
      commitTextUpdate(textInstance, oldText, newText);
      return;
    }
    case HostRoot: {
      return;
    }
    case Profiler: {
      return;
    }
    case SuspenseComponent: {
      let newState: SuspenseState | null = finishedWork.memoizedState;

      let newDidTimeout;
      let primaryChildParent = finishedWork;
      if (newState === null) {
        newDidTimeout = false;
      } else {
        newDidTimeout = true;
        primaryChildParent = finishedWork.child;
        if (newState.timedOutAt === NoWork) {
          // If the children had not already timed out, record the time.
          // This is used to compute the elapsed time during subsequent
          // attempts to render the children.
          newState.timedOutAt = requestCurrentTime();
        }
      }

      if (primaryChildParent !== null) {
        hideOrUnhideAllChildren(primaryChildParent, newDidTimeout);
      }
      return;
    }
    case IncompleteClassComponent: {
      return;
    }
    default: {
      invariant(
        false,
        'This unit of work tag should not have side-effects. This error is ' +
          'likely caused by a bug in React. Please file an issue.',
      );
    }
  }
}

  • 进入 commitUpdate

    // packages/react-dom/src/client/ReactDOMHostConfig.js#L324
export function commitUpdate(
  domElement: Instance,
  updatePayload: Array<mixed>,
  type: string,
  oldProps: Props,
  newProps: Props,
  internalInstanceHandle: Object,
): void {
  // Update the props handle so that we know which props are the ones with
  // with current event handlers.
  updateFiberProps(domElement, newProps); // 将新的props挂载到新的属性上
  // Apply the diff to the DOM node.
  updateProperties(domElement, updatePayload, type, oldProps, newProps);
}

// packages/react-dom/src/client/ReactDOMComponentTree.js#L85
export function updateFiberProps(node, props) {
  node[internalEventHandlersKey] = props;
}

// packages/react-dom/src/client/ReactDOMComponent.js#L775
// Apply the diff.
export function updateProperties(
  domElement: Element,
  updatePayload: Array<any>,
  tag: string,
  lastRawProps: Object,
  nextRawProps: Object,
): void {
  // Update checked *before* name.
  // In the middle of an update, it is possible to have multiple checked.
  // When a checked radio tries to change name, browser makes another radio's checked false.
  // 像是 radio 可以设置 value 绑定来设置
  // 对于radio标签，设置通过 value 的绑定来进行是否选中的控制, 相当于是要把value转化成哪一个radio标签，它的checked属性是等于true的这么一种情况
  // 这是为什么当初在执行 diff property 的时候，判断如果这个标签是input，它的 updatePayload 直接等于了一个空数组
  // 也就是说，即便我们后续 updatePayload 的里面没有放任何的内容，但它返回的仍然是一个空数组，仍然要执行到我们这个 updateProperties 方法里面
  // 因为最终我们要去根据一些不同的情况来更新，像radio标签，checkbox 标签 的一个 checked 相关的一些状态
  if (
    tag === 'input' &&
    nextRawProps.type === 'radio' &&
    nextRawProps.name != null
  ) {
    ReactDOMInput.updateChecked(domElement, nextRawProps);
  }

  const wasCustomComponentTag = isCustomComponent(tag, lastRawProps);
  const isCustomComponentTag = isCustomComponent(tag, nextRawProps);
  // Apply the diff.
  // 更新 dom 节点的 properties
  updateDOMProperties(
    domElement,
    updatePayload,
    wasCustomComponentTag,
    isCustomComponentTag,
  );

  // TODO: Ensure that an update gets scheduled if any of the special props
  // changed.
  // 表单标签的处理
  // 其实就是把这些 input, textarea, select 标签, 特殊的一些属性，一些 attribute 给它进行一个更新的一个过程
  switch (tag) {
    case 'input':
      // Update the wrapper around inputs *after* updating props. This has to
      // happen after `updateDOMProperties`. Otherwise HTML5 input validations
      // raise warnings and prevent the new value from being assigned.
      ReactDOMInput.updateWrapper(domElement, nextRawProps);
      break;
    case 'textarea':
      ReactDOMTextarea.updateWrapper(domElement, nextRawProps);
      break;
    case 'select':
      //