completeWork

1 ）概述

• 在 completeUnitOfWork 当中，在节点是正常渲染没有任何出错的情况下
• 会去调用 completework，对这个节点进行一个完成工作的一系列操作
• 在update各种component的时候，执行了各种获取context相关的内容
• 对于 completeWork，我们会把它对应的这些节点获取的context再pop出来
• 相当于 beginWork是一个正向的流程, 而completeWork 是一个反向的流程
• 正向的流程获取的内容，反向的流程给它依次pop出来
• 最终能够达到一个再被清空的一个流程
• 对于 HostComponent 会执行一个节点的初始化以及更新的一个操作
• 然后会初始化监听事件

2 ）源码

定位到 packages/react-reconciler/src/ReactFiberCompleteWork.js#L540

进入 completeWork

function completeWork(current: Fiber | null,workInProgress: Fiber,renderExpirationTime: ExpirationTime,
): Fiber | null {// 获取当前 propsconst newProps = workInProgress.pendingProps;// 这里和 beginWork 里面的代码很像// 在这里面，很多的组件是没有任何的一个工作要做的// 相对于 class component，它也只需要去pop之前可能push进去过的一些内容switch (workInProgress.tag) {case IndeterminateComponent:break;case LazyComponent:break;case SimpleMemoComponent:case FunctionComponent:break;case ClassComponent: {const Component = workInProgress.type;if (isLegacyContextProvider(Component)) {popLegacyContext(workInProgress);}break;}// 对于 HostRoot，它也是各种 pop，因为 HostRoot 它会获取很多的一些内容case HostRoot: {popHostContainer(workInProgress);popTopLevelLegacyContextObject(workInProgress);const fiberRoot = (workInProgress.stateNode: FiberRoot);if (fiberRoot.pendingContext) {fiberRoot.context = fiberRoot.pendingContext;fiberRoot.pendingContext = null;}if (current === null || current.child === null) {// If we hydrated, pop so that we can delete any remaining children// that weren't hydrated.popHydrationState(workInProgress);// This resets the hacky state to fix isMounted before committing.// TODO: Delete this when we delete isMounted and findDOMNode.workInProgress.effectTag &= ~Placement;}// 最终它这边执行了一个叫做 updateHostContainer 这个方法// 那么这个方法在 react-dom 的环境下面是一个空的方法updateHostContainer(workInProgress);break;}// 最复杂的是 HostComponent 处理case HostComponent: {popHostContext(workInProgress);const rootContainerInstance = getRootHostContainer();const type = workInProgress.type;if (current !== null && workInProgress.stateNode != null) {updateHostComponent(current,workInProgress,type,newProps,rootContainerInstance,);if (current.ref !== workInProgress.ref) {markRef(workInProgress);}} else {if (!newProps) {invariant(workInProgress.stateNode !== null,'We must have new props for new mounts. This error is likely ' +'caused by a bug in React. Please file an issue.',);// This can happen when we abort work.break;}const currentHostContext = getHostContext();// TODO: Move createInstance to beginWork and keep it on a context// "stack" as the parent. Then append children as we go in beginWork// or completeWork depending on we want to add then top->down or// bottom->up. Top->down is faster in IE11.let wasHydrated = popHydrationState(workInProgress);if (wasHydrated) {// TODO: Move this and createInstance step into the beginPhase// to consolidate.if (prepareToHydrateHostInstance(workInProgress,rootContainerInstance,currentHostContext,)) {// If changes to the hydrated node needs to be applied at the// commit-phase we mark this as such.markUpdate(workInProgress);}} else {let instance = createInstance(type,newProps,rootContainerInstance,currentHostContext,workInProgress,);appendAllChildren(instance, workInProgress, false, false);// Certain renderers require commit-time effects for initial mount.// (eg DOM renderer supports auto-focus for certain elements).// Make sure such renderers get scheduled for later work.if (finalizeInitialChildren(instance,type,newProps,rootContainerInstance,currentHostContext,)) {markUpdate(workInProgress);}workInProgress.stateNode = instance;}if (workInProgress.ref !== null) {// If there is a ref on a host node we need to schedule a callbackmarkRef(workInProgress);}}break;}// HostText 的处理case HostText: {let newText = newProps;if (current && workInProgress.stateNode != null) {const oldText = current.memoizedProps;// If we have an alternate, that means this is an update and we need// to schedule a side-effect to do the updates.updateHostText(current, workInProgress, oldText, newText);} else {if (typeof newText !== 'string') {invariant(workInProgress.stateNode !== null,'We must have new props for new mounts. This error is likely ' +'caused by a bug in React. Please file an issue.',);// This can happen when we abort work.}const rootContainerInstance = getRootHostContainer();const currentHostContext = getHostContext();let wasHydrated = popHydrationState(workInProgress);if (wasHydrated) {if (prepareToHydrateHostTextInstance(workInProgress)) {markUpdate(workInProgress);}} else {workInProgress.stateNode = createTextInstance(newText,rootContainerInstance,currentHostContext,workInProgress,);}}break;}case ForwardRef:break;// SuspenseComponent 的处理case SuspenseComponent: {const nextState = workInProgress.memoizedState;if ((workInProgress.effectTag & DidCapture) !== NoEffect) {// Something suspended. Re-render with the fallback children.workInProgress.expirationTime = renderExpirationTime;// Do not reset the effect list.return workInProgress;}const nextDidTimeout = nextState !== null;const prevDidTimeout = current !== null && current.memoizedState !== null;if (current !== null && !nextDidTimeout && prevDidTimeout) {// We just switched from the fallback to the normal children. Delete// the fallback.// TODO: Would it be better to store the fallback fragment on// the stateNode during the begin phase?const currentFallbackChild: Fiber | null = (current.child: any).sibling;if (currentFallbackChild !== null) {// Deletions go at the beginning of the return fiber's effect listconst first = workInProgress.firstEffect;if (first !== null) {workInProgress.firstEffect = currentFallbackChild;currentFallbackChild.nextEffect = first;} else {workInProgress.firstEffect = workInProgress.lastEffect = currentFallbackChild;currentFallbackChild.nextEffect = null;}currentFallbackChild.effectTag = Deletion;}}// The children either timed out after previously being visible, or// were restored after previously being hidden. Schedule an effect// to update their visiblity.if (//nextDidTimeout !== prevDidTimeout ||// Outside concurrent mode, the primary children commit in an// inconsistent state, even if they are hidden. So if they are hidden,// we need to schedule an effect to re-hide them, just in case.((workInProgress.effectTag & ConcurrentMode) === NoContext &&nextDidTimeout)) {workInProgress.effectTag |= Update;}break;}case Fragment:break;case Mode:break;case Profiler:break;// 后续可以看到每一个基本上都是pop出来一些container，还有context相关的东西case HostPortal:popHostContainer(workInProgress);updateHostContainer(workInProgress);break;case ContextProvider:// Pop provider fiberpopProvider(workInProgress);break;case ContextConsumer:break;case MemoComponent:break;case IncompleteClassComponent: {// Same as class component case. I put it down here so that the tags are// sequential to ensure this switch is compiled to a jump table.const Component = workInProgress.type;if (isLegacyContextProvider(Component)) {popLegacyContext(workInProgress);}break;}default:invariant(false,'Unknown unit of work tag. This error is likely caused by a bug in ' +'React. Please file an issue.',);}return null;
}

• 关于 updateHostContainer, 不仅是这个方法，下面的方法
  • appendAllChildren
  • updateHostComponent
  • updateHostText
• 以上4个，会根据环境的不同来执行不同的操作
• 在 ReactDOMHostConfig.js 中 supportsMutation 为true
  • 这时候 updateHostContainer 就是一个空的方法
• 这里主要关注，HostComponent 以及 HostText，在 completeWork 中的操作
• 在这里，目前只看大致的流程，后续会对细节做具体的分析