React16源码: React中的completeWork对HostComponent处理的源码实现

HostComponent

1 ）概述

• 在 completeWork 当中，我们需要对 HostComponent 的一些操作有哪些?
  • 首先在一次更新而不是初次渲染的情况下
  • 需要去 diffProperties 来计算，需要更新的内容
  • 也就是在 vdom 中去进行一个对比来判断这一个节点是否需要真的去更新它
  • 以此来最低程度的去更新整个 dom 的一个过程
  • 对于不同 dom property，它有一些不同的处理方式

2 ）源码

定位到 packages/react-reconciler/src/ReactFiberCompleteWork.js#L581

找到 case HostComponent文章来源地址https://www.toymoban.com/news/detail-818277.html

case HostComponent: {
  // 跳过
  popHostContext(workInProgress);
  // 跳过
  const rootContainerInstance = getRootHostContainer();
  const type = workInProgress.type;
  // 不是第一次渲染，也就是更新的时候
  if (current !== null && workInProgress.stateNode != null) {
    updateHostComponent(
      current,
      workInProgress,
      type,
      newProps,
      rootContainerInstance,
    );

    if (current.ref !== workInProgress.ref) {
      markRef(workInProgress); // 跳过
    }
  } else {
    // 第一次挂载渲染
    // 没有 props 说明有问题，提示
    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;
    }
    // 跳过
    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 {
      // 第一次挂载
      // 注意，这里，创建 element的过程
      let instance = createInstance(
        type,
        newProps,
        rootContainerInstance,
        currentHostContext,
        workInProgress,
      );

      // 第一次渲染，要添加子节点
      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 (
        // 主要功能: 对dom节点上面的可能的事件监听，需要初始化整个react的事件体系
        // 这个函数返回当前节点 是否需要 autoFocus
        finalizeInitialChildren(
          instance,
          type,
          newProps,
          rootContainerInstance,
          currentHostContext,
        )
      ) {
        // 如果上面if最终是 autofocus, 就要在这个 workInProgress 上面去增加 Update 的 SideEffect
        // 来告诉后续commit的时候要执行一定的操作
        markUpdate(workInProgress);
      }
      workInProgress.stateNode = instance; // 挂载 instance
    }

    if (workInProgress.ref !== null) {
      // If there is a ref on a host node we need to schedule a callback
      markRef(workInProgress);
    }
  }
  break;
}

• 进入 createInstance

  // packages/react-dom/src/client/ReactDOMHostConfig.js#L167
  // 这个方法就是创建节点的过程
  export function createInstance(
    type: string,
    props: Props,
    rootContainerInstance: Container,
    hostContext: HostContext,
    internalInstanceHandle: Object,
  ): Instance {
    let parentNamespace: string;
    if (__DEV__) {
      // TODO: take namespace into account when validating.
      const hostContextDev = ((hostContext: any): HostContextDev);
      validateDOMNesting(type, null, hostContextDev.ancestorInfo);
      if (
        typeof props.children === 'string' ||
        typeof props.children === 'number'
      ) {
        const string = '' + props.children;
        const ownAncestorInfo = updatedAncestorInfo(
          hostContextDev.ancestorInfo,
          type,
        );
        validateDOMNesting(null, string, ownAncestorInfo);
      }
      parentNamespace = hostContextDev.namespace;
    } else {
      parentNamespace = ((hostContext: any): HostContextProd);
    }
    // 主要在这里
    const domElement: Instance = createElement(
      type,
      props,
      rootContainerInstance,
      parentNamespace,
    );
    // 后面会进入这个方法
    precacheFiberNode(internalInstanceHandle, domElement);
    // 同上
    updateFiberProps(domElement, props);
    return domElement;
  }
  

  • 进入 createElement

    // 不展开这个方法里面调用的内容
    export function createElement(
      type: string,
      props: Object,
      rootContainerElement: Element | Document,
      parentNamespace: string,
    ): Element {
      let isCustomComponentTag;
    
      // We create tags in the namespace of their parent container, except HTML
      // tags get no namespace.
      // 先要获取 document, 先要通过 document 的api来创建
      const ownerDocument: Document = getOwnerDocumentFromRootContainer(
        rootContainerElement,
      );
      let domElement: Element;
      let namespaceURI = parentNamespace;
      // 在React中有区分，不同节点类型，都会有一个定义，比如html普通节点, svg节点等
      if (namespaceURI === HTML_NAMESPACE) {
        namespaceURI = getIntrinsicNamespace(type);
      }
      // 如果是 html 类型节点，做一些特殊处理
      if (namespaceURI === HTML_NAMESPACE) {
        if (__DEV__) {
          isCustomComponentTag = isCustomComponent(type, props);
          // Should this check be gated by parent namespace? Not sure we want to
          // allow <SVG> or <mATH>.
          warning(
            isCustomComponentTag || type === type.toLowerCase(),
            '<%s /> is using incorrect casing. ' +
              'Use PascalCase for React components, ' +
              'or lowercase for HTML elements.',
            type,
          );
        }
        // 对script节点进行特殊处理
        if (type === 'script') {
          // Create the script via .innerHTML so its "parser-inserted" flag is
          // set to true and it does not execute
          const div = ownerDocument.createElement('div');
          div.innerHTML = '<script><' + '/script>'; // eslint-disable-line
          // This is guaranteed to yield a script element.
          const firstChild = ((div.firstChild: any): HTMLScriptElement);
          domElement = div.removeChild(firstChild);
        } else if (typeof props.is === 'string') {
          // $FlowIssue `createElement` should be updated for Web Components
          domElement = ownerDocument.createElement(type, {is: props.is});
        } else {
          // Separate else branch instead of using `props.is || undefined` above because of a Firefox bug.
          // See discussion in https://github.com/facebook/react/pull/6896
          // and discussion in https://bugzilla.mozilla.org/show_bug.cgi?id=1276240
          domElement = ownerDocument.createElement(type);
          // Normally attributes are assigned in `setInitialDOMProperties`, however the `multiple`
          // attribute on `select`s needs to be added before `option`s are inserted. This prevents
          // a bug where the `select` does not scroll to the correct option because singular
          // `select` elements automatically pick the first item.
          // See https://github.com/facebook/react/issues/13222
          if (type === 'select' && props.multiple) {
            const node = ((domElement: any): HTMLSelectElement);
            node.multiple = true;
          }
        }
      } else {
        domElement = ownerDocument.createElementNS(namespaceURI, type);
      }
    
      if (__DEV__) {
        if (namespaceURI === HTML_NAMESPACE) {
          if (
            !isCustomComponentTag &&
            Object.prototype.toString.call(domElement) ===
              '[object HTMLUnknownElement]' &&
            !Object.prototype.hasOwnProperty.call(warnedUnknownTags, type)
          ) {
            warnedUnknownTags[type] = true;
            warning(
              false,
              'The tag <%s> is unrecognized in this browser. ' +
                'If you meant to render a React component, start its name with ' +
                'an uppercase letter.',
              type,
            );
          }
        }
      }
    
      return domElement;
    }
    

  • 进入 precacheFiberNode

    const internalInstanceKey = '__reactInternalInstance$' + randomKey;
    
    // 就是在node上挂载上述属性
    // hostInst, node 对应着 internalInstanceHandle, domElement
    // 相当于在 对应dom节点上，通过 internalInstanceKey 这个 key
    // 去创建一个指向 fiber 对象的引用
    // 后期，我们想要从dom对象上获取对应的 fiber就可以方便获取
    export function precacheFiberNode(hostInst, node) {
      node[internalInstanceKey] = hostInst;
    }
    

  • 进入 updateFiberProps

    const internalEventHandlersKey = '__reactEventHandlers$' + randomKey;
    
    // 两个参数 node 和 props, 对应着 domElement, props
    // 在 domElement 上用一个key 存储 props
    // props 会对应到上面 domElement 的 attribute, 所以，有对应关系，方便后期取用
    export function updateFiberProps(node, props) {
      node[internalEventHandlersKey] = props;
    }
    

• 进入 appendAllChildren

  appendAllChildren = function(
    parent: Instance,
    workInProgress: Fiber,
    needsVisibilityToggle: boolean,
    isHidden: boolean,
  ) {
    // We only have the top Fiber that was created but we need recurse down its
    // children to find all the terminal nodes.
    let node = workInProgress.child;
    // 这个循环的意义：对当前节点下寻找第一层的dom节点或text节点，不会append 嵌套(继续下一层)的dom节点
    // 这样做的原因，因为对每个dom节点都会有这样一个执行 completeWork 的阶段
    // 也就是当前层只找自己下一层的dom或text, 一层一层的向下找，不会存在忽略的问题
    while (node !== null) {
      if (node.tag === HostComponent || node.tag === HostText) {
        // 注意这里，挂载节点 
        // parent 是刚刚创建的 instance
        // node.stateNode 是当前节点子节点对应的Fiber对象
        // 如果说，它的子节点那一层上面发现了原生dom节点或者文本节点，就把它挂载到节点上面
        appendInitialChild(parent, node.stateNode);
      } else if (node.tag === HostPortal) {
        // If we have a portal child, then we don't want to traverse
        // down its children. Instead, we'll get insertions from each child in
        // the portal directly.
      } else if (node.child !== null) {
        // 向下遍历
        node.child.return = node;
        node = node.child;
        continue;
      }
      // 这里直接 return
      if (node === workInProgress) {
        return;
      }
      // 没有兄弟节点，向上遍历
      while (node.sibling === null) {
        if (node.return === null || node.return === workInProgress) {
          return;
        }
        node = node.return;
      }
      // 这个本来如此，对sibling进行挂载操作
      node.sibling.return = node.return;
      // 循环找 sibling 节点
      node = node.sibling;
    }
  };
  

  • 进入 appendInitialChild

    // 这个函数执行的就是 dom 节点的 appendChild方法
    export function appendInitialChild(
      parentInstance: Instance,
      child: Instance | TextInstance,
    ): void {
      parentInstance.appendChild(child);
    }
    

• 进入 finalizeInitialChildren

  export function finalizeInitialChildren(
    domElement: Instance,
    type: string,
    props: Props,
    rootContainerInstance: Container,
    hostContext: HostContext,
  ): boolean {
    // 做了初始化事件监听，对创建的节点根据 props 设置对应的 attribute 的封装
    setInitialProperties(domElement, type, props, rootContainerInstance);
    // 返回该节点是否需要 autoFocus
    return shouldAutoFocusHostComponent(type, props);
  }
  

  • 进入 setInitialProperties

    export function setInitialProperties(
      domElement: Element,
      tag: string,
      rawProps: Object,
      rootContainerElement: Element | Document,
    ): void {
      const isCustomComponentTag = isCustomComponent(tag, rawProps);
      if (__DEV__) {
        validatePropertiesInDevelopment(tag, rawProps);
        if (
          isCustomComponentTag &&
          !didWarnShadyDOM &&
          (domElement: any).shadyRoot
        ) {
          warning(
            false,
            '%s is using shady DOM. Using shady DOM with React can ' +
              'cause things to break subtly.',
            getCurrentFiberOwnerNameInDevOrNull() || 'A component',
          );
          didWarnShadyDOM = true;
        }
      }
    
      // TODO: Make sure that we check isMounted before firing any of these events.
      let props: Object;
      // 看下面的 switch 大部分都是绑定事件
      // 大部分都是绑定事件，这个叫做 trapBubbledEvent ，这个方法就是用来绑定事件的
      // react它有一个自己开发的事件体系，它是在dom的事件体系上面去包装了一层
      // 比如说他这边传入了这个 TOP_LOAD 
      // 它有一些事件类型，它会区分不同的一些事件类型来进行一个不同的事件绑定的方式，然后会有很多的事件的一个依赖关系
      // 可以看到这边有各种各样的不同的事件绑定。比如说 TOP_ERROR, TOP_TOGGLE, TOP_INVALID, TOP_SUBMIT
      // 对于input标签，option，select，taxtarea 都会调用对应的处理程序，如 ReactDOMInput, ReactDOMTextarea等
      // 它们都有一定的封装，因为对于这些，我们认为它是一个交互组件，就是我们要进行一些输入用户操作的一些组件
      // 比如说，input它调用的这个方法叫做 ReactDOMInput.initWrapperState 这个方法
      switch (tag) {
        case 'iframe':
        case 'object':
          trapBubbledEvent(TOP_LOAD, domElement);
          props = rawProps;
          break;
        case 'video':
        case 'audio':
          // Create listener for each media event
          for (let i = 0; i < mediaEventTypes.length; i++) {
            trapBubbledEvent(mediaEventTypes[i], domElement);
          }
          props = rawProps;
          break;
        case 'source':
          trapBubbledEvent(TOP_ERROR, domElement);
          props = rawProps;
          break;
        case 'img':
        case 'image':
        case 'link':
          trapBubbledEvent(TOP_ERROR, domElement);
          trapBubbledEvent(TOP_LOAD, domElement);
          props = rawProps;
          break;
        case 'form':
          trapBubbledEvent(TOP_RESET, domElement);
          trapBubbledEvent(TOP_SUBMIT, domElement);
          props = rawProps;
          break;
        case 'details':
          trapBubbledEvent(TOP_TOGGLE, domElement);
          props = rawProps;
          break;
        case 'input':
          ReactDOMInput.initWrapperState(domElement, rawProps);
          props = ReactDOMInput.getHostProps(domElement, rawProps);
          trapBubbledEvent(TOP_INVALID, domElement);
          // For controlled components we always need to ensure we're listening
          // to onChange. Even if there is no listener.
          ensureListeningTo(rootContainerElement, 'onChange');
          break;
        case 'option':
          ReactDOMOption.validateProps(domElement, rawProps);
          props = ReactDOMOption.getHostProps(domElement, rawProps);
          break;
        case 'select':
          ReactDOMSelect.initWrapperState(domElement, rawProps);
          props = ReactDOMSelect.getHostProps(domElement, rawProps);
          trapBubbledEvent(TOP_INVALID, domElement);
          // For controlled components we always need to ensure we're listening
          // to onChange. Even if there is no listener.
          ensureListeningTo(rootContainerElement, 'onChange');
          break;
        case 'textarea':
          ReactDOMTextarea.initWrapperState(domElement, rawProps);
          props = ReactDOMTextarea.getHostProps(domElement, rawProps);
          trapBubbledEvent(TOP_INVALID, domElement);
          // For controlled components we always need to ensure we're listening
          // to onChange. Even if there is no listener.
          ensureListeningTo(rootContainerElement, 'onChange');
          break;
        default:
          props = rawProps;
      }
    
      // 验证 props 并给出提醒
      assertValidProps(tag, props);
    
      // 初始化dom的属性相关逻辑
      setInitialDOMProperties(
        tag,
        domElement,
        rootContainerElement,
        props,
        isCustomComponentTag,
      );
    
      switch (tag) {
        case 'input':
          // TODO: Make sure we check if this is still unmounted or do any clean
          // up necessary since we never stop tracking anymore.
          inputValueTracking.track((domElement: any));
          ReactDOMInput.postMountWrapper(domElement, rawProps, false);
          break;
        case 'textarea':
          // TODO: Make sure we check if this is still unmounted or do any clean
          // up necessary since we never stop tracking anymore.
          inputValueTracking.track((domElement: any));
          ReactDOMTextarea.postMountWrapper(domElement, rawProps);
          break;
        case 'option':
          ReactDOMOption.postMountWrapper(domElement, rawProps);
          break;
        case 'select':
          ReactDOMSelect.postMountWrapper(domElement, rawProps);
          break;
        default:
          if (typeof props.onClick === 'function') {
            // TODO: This cast may not be sound for SVG, MathML or custom elements.
            trapClickOnNonInteractiveElement(((domElement: any): HTMLElement));
          }
          break;
      }
    }
    

    • 进入 ReactDOMInput.initWrapperState

      // packages/react-dom/src/client/ReactDOMInput.js
      export function initWrapperState(element: Element, props: Object) {
        // 跳过 DEV
        if (__DEV__) {
          ReactControlledValuePropTypes.checkPropTypes('input', props);
      
          if (
            props.checked !== undefined &&
            props.defaultChecked !== undefined &&
            !didWarnCheckedDefaultChecked
          ) {
            warning(
              false,
              '%s contains an input of type %s with both checked and defaultChecked props. ' +
                'Input elements must be either controlled or uncontrolled ' +
                '(specify either the checked prop, or the defaultChecked prop, but not ' +
                'both). Decide between using a controlled or uncontrolled input ' +
                'element and remove one of these props. More info: ' +
                'https://fb.me/react-controlled-components',
              getCurrentFiberOwnerNameInDevOrNull() || 'A component',
              props.type,
            );
            didWarnCheckedDefaultChecked = true;
          }
          if (
            props.value !== undefined &&
            props.defaultValue !== undefined &&
            !didWarnValueDefaultValue
          ) {
            warning(
              false,
              '%s contains an input of type %s with both value and defaultValue props. ' +
                'Input elements must be either controlled or uncontrolled ' +
                '(specify either the value prop, or the defaultValue prop, but not ' +
                'both). Decide between using a controlled or uncontrolled input ' +
                'element and remove one of these props. More info: ' +
                'https://fb.me/react-controlled-components',
              getCurrentFiberOwnerNameInDevOrNull() || 'A component',
              props.type,
            );
            didWarnValueDefaultValue = true;
          }
        }
      
      
        const node = ((element: any): InputWithWrapperState);
      
        // 关于 defaultValue, 如果不希望使用value来绑定input它的一个值
        // 如果绑定了value这个值，我们input的value，只能通过 setState 这个value的值来进行一个变更
        // 如果我们没有绑定事件，那么我们在input里面输入是不会有任何变化的
        // 那这个时候我们如果要有初始的值，又不希望去绑定 value
        // 可以通过使用 defaultValue，如果没有 defaultvalue 它就是一个空的
        const defaultValue = props.defaultValue == null ? '' : props.defaultValue;
      
        // 在input对应的dom节点上面呢去挂载了一个属性，叫做 _wrapperState
        // 它里面定义了3个属性
        node._wrapperState = {
          initialChecked:
            props.checked != null ? props.checked : props.defaultChecked,
          initialValue: getToStringValue(
            props.value != null ? props.value : defaultValue,
          ),
          controlled: isControlled(props),
        };
      }
      

      • 进入 isControlled

        // 处理 checkbox 和 radio
        function isControlled(props) {
          const usesChecked = props.type === 'checkbox' || props.type === 'radio';
          return usesChecked ? props.checked != null : props.value != null;
        }
        

    • 进入 getHostProps

      export function getHostProps(element: Element, props: Object) {
        const node = ((element: any): InputWithWrapperState);
        const checked = props.checked;
        // 组合 props
        const hostProps = Object.assign({}, props, {
          defaultChecked: undefined,
          defaultValue: undefined,
          value: undefined,
          checked: checked != null ? checked : node._wrapperState.initialChecked,
        });
      
        return hostProps;
      }
      

    • 对于 assertValidProps 和 setInitialDOMProperties
      • 这样两项封装的Dom操作细节处理，不展开
      • 前者做提示处理，后者做dom操作
  • 进入 shouldAutoFocusHostComponent

    function shouldAutoFocusHostComponent(type: string, props: Props): boolean {
      // 对可以 focus 的 dom节点进行 bool 处理，注意，这里没有 break
      switch (type) {
        case 'button':
        case 'input':
        case 'select':
        case 'textarea':
          return !!props.autoFocus;
      }
      return false;
    }
    

• 进入 markUpdate

  // 标记 Update 这个 SideEffect
  function markUpdate(workInProgress: Fiber) {
    // Tag the fiber with an update effect. This turns a Placement into
    // a PlacementAndUpdate.
    workInProgress.effectTag |= Update;
  }
  

• 关于 更新时的 updateHostComponent 这块后续单独拿出来说

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