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PortalComponent

1 ）概述

• React Portal之所以叫Portal，因为做的就是和“传送门”一样的事情
• render到一个组件里面去，实际改变的是网页上另一处的DOM结构
• 主要关注 portal的创建, 调和, 更新过程

2 ）源码

定位到 packages/react-dom/src/client/ReactDOM.js#L576

function createPortal(children: ReactNodeList,container: DOMContainer,key: ?string = null,
) {invariant(isValidContainer(container),'Target container is not a DOM element.',);// TODO: pass ReactDOM portal implementation as third argumentreturn ReactPortal.createPortal(children, container, null, key);
}

• 这里调用的是 ReactPortal.createPortal, 进入

  // packages/shared/ReactPortal.js#L14
  export function createPortal(children: ReactNodeList,containerInfo: any,// TODO: figure out the API for cross-renderer implementation.implementation: any,key: ?string = null,
  ): ReactPortal {return {// This tag allow us to uniquely identify this as a React Portal$$typeof: REACT_PORTAL_TYPE,key: key == null ? null : '' + key,children,containerInfo, // dom 挂载节点implementation,};
  }
  

  • 这里返回一个对象，类似于 ReactElement
  • 区别在于 $$typeof 和 containerInfo 需要的挂载点

• 对于 REACT_PORTAL_TYPE 类型的组件在 reconcile 时, 看下具体操作, 找到 reconcileSinglePortal

  // packages/react-reconciler/src/ReactChildFiber.js#L1171
  function reconcileSinglePortal(returnFiber: Fiber,currentFirstChild: Fiber | null,portal: ReactPortal,expirationTime: ExpirationTime,
  ): Fiber {const key = portal.key; // 当前的 keylet child = currentFirstChild;// 如果 存在 child, 对比 child.key === keywhile (child !== null) {// TODO: If key === null and child.key === null, then this only applies to// the first item in the list.if (child.key === key) {// 关注这里，有 containerInfo 的对比，portal 需要关心渲染到的节点是否有变化// 如果节点有变化，那么这个 portal 的渲染过程也会有变化// 都符合，说明老节点都可以复用if (child.tag === HostPortal &&child.stateNode.containerInfo === portal.containerInfo &&child.stateNode.implementation === portal.implementation) {deleteRemainingChildren(returnFiber, child.sibling); // 删除其他节点// 通过 useFiber 复用这个节点const existing = useFiber(child,portal.children || [],expirationTime,);existing.return = returnFiber;return existing;} else {// key相同，但是不符合上述if, 没法复用，删除干净deleteRemainingChildren(returnFiber, child);break;}} else {// key 不同，删除当前节点deleteChild(returnFiber, child);}child = child.sibling;}// 创建一个 portal 的 fiber 对象const created = createFiberFromPortal(portal,returnFiber.mode,expirationTime,);created.return = returnFiber;return created;
  }
  

• 对于更新一个portal节点，进入 updatePortalComponent

  // packages/react-reconciler/src/ReactFiberBeginWork.js#L1322
  function updatePortalComponent(current: Fiber | null,workInProgress: Fiber,renderExpirationTime: ExpirationTime,
  ) {// 挂载点处理pushHostContainer(workInProgress, workInProgress.stateNode.containerInfo);const nextChildren = workInProgress.pendingProps; // 这里 pendingProps 是 childrenif (current === null) {// Portals are special because we don't append the children during mount// but at commit. Therefore we need to track insertions which the normal// flow doesn't do during mount. This doesn't happen at the root because// the root always starts with a "current" with a null child.// TODO: Consider unifying this with how the root works.workInProgress.child = reconcileChildFibers(workInProgress,null,nextChildren,renderExpirationTime,);} else {reconcileChildren(current,workInProgress,nextChildren,renderExpirationTime,);}return workInProgress.child;
  }
  

  • 之前梳理过的 API 不再赘述
  • 一些API的调用，在源码的注释中