React16源码: React中的completeWork对HostText处理含更新的源码实现

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HostText

1 ）概述

在 completeWork 中对 HostText的处理
在第一次挂载和后续更新的不同条件下进行操作
- 第一次挂载主要是创建实例
- 后续更新其实也是重新创建实例

2 ）源码

定位到 packages/react-reconciler/src/ReactFiberCompleteWork.js#L663

到 case HostText 这里

case HostText: {let newText = newProps;// 符合这个条件，说明它不是第一次渲染，就是更新的状态// 调用 updateHostText 进行更新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 {// 对于第一次渲染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.}// 跳过 context 处理const rootContainerInstance = getRootHostContainer();const currentHostContext = getHostContext();// 跳过 hydrate 处理let wasHydrated = popHydrationState(workInProgress);if (wasHydrated) {if (prepareToHydrateHostTextInstance(workInProgress)) {markUpdate(workInProgress);}} else {// 创建 文本 实例workInProgress.stateNode = createTextInstance(newText,rootContainerInstance,currentHostContext,workInProgress,);}}break;
}

进入 updateHostText

updateHostText = function(current: Fiber,workInProgress: Fiber,oldText: string,newText: string,
) {// 这个非常简单，通过前后 text 是否有区别// 如果不同，则创建新的 text实例if (oldText !== newText) {// If the text content differs, we'll create a new text instance for it.// 先跳过 context 的处理const rootContainerInstance = getRootHostContainer();const currentHostContext = getHostContext();workInProgress.stateNode = createTextInstance(newText,rootContainerInstance,currentHostContext,workInProgress,);// We'll have to mark it as having an effect, even though we won't use the effect for anything.// This lets the parents know that at least one of their children has changed.markUpdate(workInProgress);}
};

进入 createTextInstance

// packages/react-dom/src/client/ReactDOMHostConfig.js#L272
export function createTextInstance(text: string,rootContainerInstance: Container,hostContext: HostContext,internalInstanceHandle: Object,
): TextInstance {if (__DEV__) {const hostContextDev = ((hostContext: any): HostContextDev);validateDOMNesting(null, text, hostContextDev.ancestorInfo);}const textNode: TextInstance = createTextNode(text, rootContainerInstance);// 这个方法之前阅过precacheFiberNode(internalInstanceHandle, textNode);return textNode;
}

进入 createTextNode

export function createTextNode(text: string,rootContainerElement: Element | Document,
): Text {// 最终 getOwnerDocumentFromRootContainer 这里返回一个dom对象，调用dom的 createTextNode 这个方法return getOwnerDocumentFromRootContainer(rootContainerElement).createTextNode(text,);
}

进入 getOwnerDocumentFromRootContainer

function getOwnerDocumentFromRootContainer(rootContainerElement: Element | Document,
): Document {// rootContainerElement.ownerDocument 这里是 window.document 对象// 这么做是为了兼容多平台api的使用return rootContainerElement.nodeType === DOCUMENT_NODE? (rootContainerElement: any): rootContainerElement.ownerDocument;
}