FiberNode

V16

每一个ReactElement对应一个Fiber对象，记录各个节点的状态，由于Fiber对象并不是绑定在组件的实例上，这也给hooks实现时，拿到每个节点的状态提供了方便

Fiber 记录了整个应用的树型结构

// Fiber对应一个组件需要被处理或者已经处理了，一个组件可以有一个或者多个Fiber
type Fiber = {|
  // 标记不同的组件类型
  tag: WorkTag,

  // ReactElement里面的key
  key: null | string,

  // ReactElement.type，也就是我们调用`createElement`的第一个参数
  elementType: any,

  // The resolved function/class/ associated with this fiber.
  // 异步组件resolved之后返回的内容，一般是`function`或者`class`
  type: any,

  // The local state associated with this fiber.
  // 跟当前Fiber相关本地状态（比如浏览器环境就是DOM节点）
  stateNode: any,

  // 指向他在Fiber节点树中的`parent`，用来在处理完这个节点之后向上返回
  return: Fiber | null,

  // 单链表树结构
  // 指向自己的第一个子节点
  child: Fiber | null,
  // 指向自己的兄弟结构
  // 兄弟节点的return指向同一个父节点
  sibling: Fiber | null,
  index: number,

  // ref属性
  ref: null | (((handle: mixed) => void) & {_stringRef: ?string}) | RefObject,

  // 新的变动带来的新的props
  pendingProps: any, 
  // 上一次渲染完成之后的props
  memoizedProps: any,

  // 该Fiber对应的组件产生的Update会存放在这个队列里面
  updateQueue: UpdateQueue<any> | null,

  // 上一次渲染的时候的state
  memoizedState: any,

  // 一个列表，存放这个Fiber依赖的context
  firstContextDependency: ContextDependency<mixed> | null,

  // 用来描述当前Fiber和他子树的`Bitfield`
  // 共存的模式表示这个子树是否默认是异步渲染的
  // Fiber被创建的时候他会继承父Fiber
  // 其他的标识也可以在创建的时候被设置
  // 但是在创建之后不应该再被修改，特别是他的子Fiber创建之前
  mode: TypeOfMode,

  // Effect
  // 用来记录Side Effect
  effectTag: SideEffectTag,

  // 单链表用来快速查找下一个side effect
  nextEffect: Fiber | null,

  // 子树中第一个side effect
  firstEffect: Fiber | null,
  // 子树中最后一个side effect
  lastEffect: Fiber | null,

  // 代表任务在未来的哪个时间点应该被完成
  // 不包括他的子树产生的任务
  expirationTime: ExpirationTime,

  // 快速确定子树中是否有不在等待的变化
  childExpirationTime: ExpirationTime,

  // 在Fiber树更新的过程中，每个Fiber都会有一个跟其对应的Fiber
  // 镜像Fiber
  // 我们称他为`current <==> workInProgress`
  // 在渲染完成之后他们会交换位置
  alternate: Fiber | null,

  // 下面是调试相关的，收集每个Fiber和子树渲染时间的

  actualDuration?: number,

  // If the Fiber is currently active in the "render" phase,
  // This marks the time at which the work began.
  // This field is only set when the enableProfilerTimer flag is enabled.
  actualStartTime?: number,

  // Duration of the most recent render time for this Fiber.
  // This value is not updated when we bailout for memoization purposes.
  // This field is only set when the enableProfilerTimer flag is enabled.
  selfBaseDuration?: number,

  // Sum of base times for all descedents of this Fiber.
  // This value bubbles up during the "complete" phase.
  // This field is only set when the enableProfilerTimer flag is enabled.
  treeBaseDuration?: number,

  // Conceptual aliases
  // workInProgress : Fiber ->  alternate The alternate used for reuse happens
  // to be the same as work in progress.
  // __DEV__ only
  _debugID?: number,
  _debugSource?: Source | null,
  _debugOwner?: Fiber | null,

V17

// A Fiber is work on a Component that needs to be done or was done. There can
// be more than one per component.

// Fiber 是组件的中的工作内容，需要完成或已经完成，每个组件可以个有多个。

export type Fiber = {|
  // These first fields are conceptually members of an Instance. This used to
  // be split into a separate type and intersected with the other Fiber fields,
  // but until Flow fixes its intersection bugs, we've merged them into a
  // single type.

  // 第一个字段概念上是实例的一部分，它过去被拆分成单独的类型并且存在于其他Fiber节点的字段中。
  // 直到Flow修复了交叉错误，我们把它合并成单一类型

  // An Instance is shared between all versions of a component. We can easily
  // break this out into a separate object to avoid copying so much to the
  // alternate versions of the tree. We put this on a single object for now to
  // minimize the number of objects created during the initial render.

  // 实例在组件的所有的版本中共享，可以很容易的拆分成单个对象避免复制太多内容到镜像树上，
  // 现在我们把它放在单独的对象上，为了初始化渲染期间最小化创建对象的数量

  // Tag identifying the type of fiber.
  // fiber类型， 标签标识

  tag: WorkTag,

  // Unique identifier of this child.
  // 这个子元素的唯一标识
  key: null | string,

  // The value of element.type which is used to preserve the identity during
  // reconciliation of this child.
  // element.type的值，用于在调和子节点期间保留标识。
  elementType: any,

  // The resolved function/class/ associated with this fiber.
  // 函数组件或类组件通过type链接，type为函数组件或类组件的引用
  type: any,

  // The local state associated with this fiber.
  // 保存实例化之后的节点对象
  stateNode: any,

  // Conceptual aliases
  // parent : Instance -> return The parent happens to be the same as the
  // return fiber since we've merged the fiber and instance.

  // Remaining fields belong to Fiber

  // The Fiber to return to after finishing processing this one.
  // This is effectively the parent, but there can be multiple parents (two)
  // so this is only the parent of the thing we're currently processing.
  // It is conceptually the same as the return address of a stack frame.
  return: Fiber | null,

  // Singly Linked List Tree Structure.
  child: Fiber | null,
  sibling: Fiber | null,
  index: number,

  // The ref last used to attach this node.
  // I'll avoid adding an owner field for prod and model that as functions.
  ref:
    | null
    | (((handle: mixed) => void) & {_stringRef: ?string, ...})
    | RefObject,

  // Input is the data coming into process this fiber. Arguments. Props.
  pendingProps: any, // This type will be more specific once we overload the tag.
  memoizedProps: any, // The props used to create the output.

  // A queue of state updates and callbacks.
  updateQueue: mixed,

  // The state used to create the output
  memoizedState: any,

  // Dependencies (contexts, events) for this fiber, if it has any
  dependencies: Dependencies | null,

  // Bitfield that describes properties about the fiber and its subtree. E.g.
  // the ConcurrentMode flag indicates whether the subtree should be async-by-
  // default. When a fiber is created, it inherits the mode of its
  // parent. Additional flags can be set at creation time, but after that the
  // value should remain unchanged throughout the fiber's lifetime, particularly
  // before its child fibers are created.
  mode: TypeOfMode,

  // Effect
  flags: Flags,
  subtreeFlags: Flags,
  deletions: Array<Fiber> | null,

  // Singly linked list fast path to the next fiber with side-effects.
  nextEffect: Fiber | null,

  // The first and last fiber with side-effect within this subtree. This allows
  // us to reuse a slice of the linked list when we reuse the work done within
  // this fiber.
  firstEffect: Fiber | null,
  lastEffect: Fiber | null,

  lanes: Lanes,
  childLanes: Lanes,

  // This is a pooled version of a Fiber. Every fiber that gets updated will
  // eventually have a pair. There are cases when we can clean up pairs to save
  // memory if we need to.
  alternate: Fiber | null,

  // Time spent rendering this Fiber and its descendants for the current update.
  // This tells us how well the tree makes use of sCU for memoization.
  // It is reset to 0 each time we render and only updated when we don't bailout.
  // This field is only set when the enableProfilerTimer flag is enabled.
  actualDuration?: number,

  // If the Fiber is currently active in the "render" phase,
  // This marks the time at which the work began.
  // This field is only set when the enableProfilerTimer flag is enabled.
  actualStartTime?: number,

  // Duration of the most recent render time for this Fiber.
  // This value is not updated when we bailout for memoization purposes.
  // This field is only set when the enableProfilerTimer flag is enabled.
  selfBaseDuration?: number,

  // Sum of base times for all descendants of this Fiber.
  // This value bubbles up during the "complete" phase.
  // This field is only set when the enableProfilerTimer flag is enabled.
  treeBaseDuration?: number,

  // Conceptual aliases
  // workInProgress : Fiber ->  alternate The alternate used for reuse happens
  // to be the same as work in progress.
  // __DEV__ only

  _debugSource?: Source | null,
  _debugOwner?: Fiber | null,
  _debugIsCurrentlyTiming?: boolean,
  _debugNeedsRemount?: boolean,

  // Used to verify that the order of hooks does not change between renders.
  _debugHookTypes?: Array<HookType> | null,
|};

打赏