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

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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 commitUpdateif (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 propertiesupdateDOMProperties(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':// <select> value update needs to occur after <option> children// reconciliationReactDOMSelect.postUpdateWrapper(domElement, nextRawProps);break;}
}// packages/react-dom/src/client/ReactDOMInput.js#L128
export function updateChecked(element: Element, props: Object) {const node = ((element: any): InputWithWrapperState);const checked = props.checked;if (checked != null) {// dom操作DOMPropertyOperations.setValueForProperty(node, 'checked', checked, false);}
}// packages/react-dom/src/shared/isCustomComponent.js#L10
function isCustomComponent(tagName: string, props: Object) {// 它根据标签名字上，是否有 - 的存在, 并且 props.is 是 string 则是if (tagName.indexOf('-') === -1) {return typeof props.is === 'string';}// 有 - 的，屏蔽自有的一些，排除之后其他都算 自定义switch (tagName) {// These are reserved SVG and MathML elements.// We don't mind this whitelist too much because we expect it to never grow.// The alternative is to track the namespace in a few places which is convoluted.// https://w3c.github.io/webcomponents/spec/custom/#custom-elements-core-conceptscase 'annotation-xml':case 'color-profile':case 'font-face':case 'font-face-src':case 'font-face-uri':case 'font-face-format':case 'font-face-name':case 'missing-glyph':return false;default:return true;}
}// packages/react-dom/src/client/ReactDOMComponent.js#L326
function updateDOMProperties(domElement: Element,updatePayload: Array<any>,wasCustomComponentTag: boolean,isCustomComponentTag: boolean,
): void {// TODO: Handle wasCustomComponentTag// 遍历这个updatepaylow的这个数组，然后记住这边的下标增加是每次加2，而不是加1了for (let i = 0; i < updatePayload.length; i += 2) {// i 对应的就是 propKey, 然后i加1对应的就是 propValueconst propKey = updatePayload[i];const propValue = updatePayload[i + 1];// 如果是style，会对每一个style的属性来执行if (propKey === STYLE) {// 里面会遍历这个style对象里面的每一个style属性，然后去设置对应的值// 我们拿到一个对象，最终如何给它转换成真正的CSS属性给它设置上去的一个过程// 其中还要考虑一些属性是删除的操作CSSPropertyOperations.setValueForStyles(domElement, propValue);} else if (propKey === DANGEROUSLY_SET_INNER_HTML) {setInnerHTML(domElement, propValue);} else if (propKey === CHILDREN) {setTextContent(domElement, propValue);} else {// 对于其他属性的处理DOMPropertyOperations.setValueForProperty(domElement,propKey,propValue,isCustomComponentTag,);}}
}
// packages/react-dom/src/client/ReactDOMHostConfig.js#L343
export function commitTextUpdate(textInstance: TextInstance,oldText: string,newText: string,
): void {textInstance.nodeValue = newText;
}

对于 HostComponent 来说
- 因为更新的过程，有一大部分是放在 completeUnitOfWork 里面去做了
- 在 completeWork 的时候会获得这个 updatePayload
- 这个 payload 已经告诉我们具体要做哪些属性的操作了
- 它里面也包含了我们有一些 attribute 要删除的情况
- 就是说它的 value 为 null 的情况, 标示着这个属性是要被删除的
- 所以, 那一部分工作做完了之后，到这里其实已经比较的简单了
- 只需要根据 updatePayload 里面相关的内容进行一个整体的更新就可以了
对于 HostText 它也要进行一个更新，它调用了一个 commitTextUpdate
以上就是整个 commitWork 里面做的事情, 具体的细节写在代码注释里