前言
React Hooks 是 React16 新出的基于函数式组件的一组新的 api，其不同于之前 class 组件的内层嵌套形式，利用 hooks 进行钩子形式的对数据进行了组件间的流向组织，sdwan 我的项目中都是基于函数式组件的封装，本文为 sdwan 我的项目中的 react hooks 的利用实际
目录
- 增加正告规定弹窗组件实际
- React Hooks 源码解读
- React Fiber 数据结构剖析
摸索案例
增加正告规定弹窗组件实际
[组件目录]
-
components
- addRule.jsx
- RuleList.jsx
- index.jsx
- index.less
[目录形容] addRule 是点击弹窗后弹出的主体组件
[源码剖析] addRule 是增加规定的弹窗，其中在告警规定一栏中，须要对列表中的行进行加减操作，这里最先想到的就是利用 useState 进行数据的治理，但其实 useState 是 useReducer 的语法糖，后续源码中会剖析，咱们看到应用了 useState 后能够将所有状态抽离到顶部，后续但凡须要应用 trNum 或 setTrNum 的便能够间接应用，这样就省去了在 setState 中的设置以及对相应 this 的绑定问题，使得数据的操作更加纯正而且清晰
const AddRule = (props) => {const { children, title} = props;
......
const [trNum, setTrNum] = useState(1);
const trLoop = (n) => {let arr = [];
for(let i=0; i< n; i++) {
arr.push(
<tr>
<td>
<Select
placeholder='请抉择'
defaultValue='0'
style={{width:'120px'}}
>
{options.params.map((d) => (<Select.Option value={d.status} key={d.status}>
{d.text}
</Select.Option>
))}
</Select>
</td>
<td>
<Select
placeholder='请抉择'
defaultValue='0'
>
{options.compare.map((d) => (<Select.Option value={d.status} key={d.status}>
{d.text}
</Select.Option>
))}
</Select>
</td>
<td>
<Select
placeholder='请抉择'
defaultValue={currentType}
onChange={val => setTypeValue(val)}
>
{options.type.map((d) => (<Select.Option value={d.status} key={d.status}>
{d.text}
</Select.Option>
))}
</Select>
</td>
<td>
{typeValue == options.type[1].status
?
<span style={{display: 'inline-flex', verticalAlign: 'middle', lineHeight: '32px', width: '120px'}}>
<Input placeholder=""/>dBm
</span>
:
<Select
placeholder='请抉择'
defaultValue='0'
style={{width:'120px'}}
>
{options.params.map((d) => (<Select.Option value={d.status} key={d.status}>
{d.text}
</Select.Option>
))}
</Select>
}
</td>
<td>
<PlusOutlined style={{color: '#1890ff'}} onClick={()=>setTrNum(trNum + 1)}/>
</td>
<td>
<CloseOutlined style={{color: '#ff4d4f'}} onClick={()=> trNum>1 && setTrNum(trNum - 1)}/>
</td>
</tr>
)
};
return arr;
};
......
return (
<>
<span onClick={showModelHandler}>{children}</span>
<Modal
title={title}
visible={visible}
onCancel={hideModelHandler}
onOk={handleOk}
maskClosable={false}
destroyOnClose
>
<Form form={form} layout="vertical">
......
<Form.Item name="告警规定" label="告警规定">
<div style={{width: '100%', backgroundColor: '#ececec', padding: '10px'}}>
<span>
合乎以下 <Select
placeholder='请抉择'
defaultValue='0'
style={{width: '120px'}}
>
{options.rule.map((d) => (<Select.Option value={d.status} key={d.status}>
{d.text}
</Select.Option>
))}
</Select> 条件：</span>
<div
style={{
border: '1px solid #ccc',
width: '100%',
background: '#fff',
marginTop: '10px',
padding: '4px'
}}
>
<table >
<tbody >
{trLoop(trNum) }
</tbody>
</table>
</div>
</div>
</Form.Item>
......
</Form>
</Modal>
</>
);
};React Hooks 源码解读
[组件目录]
-
packages
-
react
-
src
- ReactHooks.js
-
-
这里仅仅是做了一个名称的导出包含：
- useContext
- useState
- useReducer
- useRef
- useEffect
- useLayoutEffect
- useCallback
- useMemo
- useImperativeHandles
- useDebugValue
- useTransition
- useDeferredValue
- useOpaqueIdentifier
- useMutableSource
这里真正的源码是放在了 packages/react-reconciler/src/ReactFiberHooks.js 里，能够看出其利用的依然是 React 的外围数据结构 Fiber 的调度作用
export function renderWithHooks<Props, SecondArg>(
current: Fiber | null,
workInProgress: Fiber,
Component: (p: Props, arg: SecondArg) => any,
props: Props,
secondArg: SecondArg,
nextRenderLanes: Lanes,
): any {
renderLanes = nextRenderLanes;
currentlyRenderingFiber = workInProgress;
if (__DEV__) {
hookTypesDev =
current !== null
? ((current._debugHookTypes: any): Array<HookType>)
: null;
hookTypesUpdateIndexDev = -1;
// Used for hot reloading:
ignorePreviousDependencies =
current !== null && current.type !== workInProgress.type;
}
workInProgress.memoizedState = null;
workInProgress.updateQueue = null;
workInProgress.lanes = NoLanes;
// The following should have already been reset
// currentHook = null;
// workInProgressHook = null;
// didScheduleRenderPhaseUpdate = false;
// TODO Warn if no hooks are used at all during mount, then some are used during update.
// Currently we will identify the update render as a mount because memoizedState === null.
// This is tricky because it's valid for certain types of components (e.g. React.lazy)
// Using memoizedState to differentiate between mount/update only works if at least one stateful hook is used.
// Non-stateful hooks (e.g. context) don't get added to memoizedState,
// so memoizedState would be null during updates and mounts.
if (__DEV__) {if (current !== null && current.memoizedState !== null) {ReactCurrentDispatcher.current = HooksDispatcherOnUpdateInDEV;} else if (hookTypesDev !== null) {
// This dispatcher handles an edge case where a component is updating,
// but no stateful hooks have been used.
// We want to match the production code behavior (which will use HooksDispatcherOnMount),
// but with the extra DEV validation to ensure hooks ordering hasn't changed.
// This dispatcher does that.
ReactCurrentDispatcher.current = HooksDispatcherOnMountWithHookTypesInDEV;
} else {ReactCurrentDispatcher.current = HooksDispatcherOnMountInDEV;}
} else {
ReactCurrentDispatcher.current =
current === null || current.memoizedState === null
? HooksDispatcherOnMount
: HooksDispatcherOnUpdate;
}
let children = Component(props, secondArg);
// Check if there was a render phase update
if (didScheduleRenderPhaseUpdateDuringThisPass) {
// Keep rendering in a loop for as long as render phase updates continue to
// be scheduled. Use a counter to prevent infinite loops.
let numberOfReRenders: number = 0;
do {
didScheduleRenderPhaseUpdateDuringThisPass = false;
invariant(
numberOfReRenders < RE_RENDER_LIMIT,
'Too many re-renders. React limits the number of renders to prevent' +
'an infinite loop.',
);
numberOfReRenders += 1;
if (__DEV__) {
// Even when hot reloading, allow dependencies to stabilize
// after first render to prevent infinite render phase updates.
ignorePreviousDependencies = false;
}
// Start over from the beginning of the list
currentHook = null;
workInProgressHook = null;
workInProgress.updateQueue = null;
if (__DEV__) {
// Also validate hook order for cascading updates.
hookTypesUpdateIndexDev = -1;
}
ReactCurrentDispatcher.current = __DEV__
? HooksDispatcherOnRerenderInDEV
: HooksDispatcherOnRerender;
children = Component(props, secondArg);
} while (didScheduleRenderPhaseUpdateDuringThisPass);
}
// We can assume the previous dispatcher is always this one, since we set it
// at the beginning of the render phase and there's no re-entrancy.
ReactCurrentDispatcher.current = ContextOnlyDispatcher;
if (__DEV__) {workInProgress._debugHookTypes = hookTypesDev;}
// This check uses currentHook so that it works the same in DEV and prod bundles.
// hookTypesDev could catch more cases (e.g. context) but only in DEV bundles.
const didRenderTooFewHooks =
currentHook !== null && currentHook.next !== null;
renderLanes = NoLanes;
currentlyRenderingFiber = (null: any);
currentHook = null;
workInProgressHook = null;
if (__DEV__) {
currentHookNameInDev = null;
hookTypesDev = null;
hookTypesUpdateIndexDev = -1;
}
didScheduleRenderPhaseUpdate = false;
invariant(
!didRenderTooFewHooks,
'Rendered fewer hooks than expected. This may be caused by an accidental' +
'early return statement.',
);
return children;
}从中抽离出外围的 hooks 渲染，其余的具体的 use 办法能够在其上进行扩大，能够看出其实质是是基于 Fiber 的 workInProgress 的全局变量的更改与调度，其中蕴含记录以后 hook 状态的 memoizedState 以及须要更新的队列 updateQueue，hooks 的队列通过 memoizedState 及 next 形成了一个链表，整个 hook 的外围是基于 Dispatcher 的切换 hook 的调用，这里就波及到 Fiber 的整个数据结构，在下一节中进行形容
React Fiber 数据结构剖析
[组件目录]
-
packages
-
react-reconciler
-
src
- ReactFiber.js
-
-
简略来说 React 的 Fiber 数据结构是保护了一个如下的数据格式：
Fiber = {
// 标识 fiber 类型的标签，详情参看下述 WorkTag
tag: WorkTag,
// 指向父节点
return: Fiber | null,
// 指向子节点
child: Fiber | null,
// 指向兄弟节点
sibling: Fiber | null,
// 在开始执行时设置 props 值
pendingProps: any,
// 在完结时设置的 props 值
memoizedProps: any,
// 以后 state
memoizedState: any,
// Effect 类型，详情查看以下 effectTag
effectTag: SideEffectTag,
// effect 节点指针，指向下一个 effect
nextEffect: Fiber | null,
// effect list 是单向链表，第一个 effect
firstEffect: Fiber | null,
// effect list 是单向链表，最初一个 effect
lastEffect: Fiber | null,
// work 的过期工夫，可用于标识一个 work 优先级程序
expirationTime: ExpirationTime,
};
该数据结构是一个通过链表实现的树的构造，整个 React 的阶段可分为 Render Phase、Pre-Commit Phase 以及 Commit Phase，Fiber 的设计初衷是利用浏览器渲染过程中残余的工夫碎片来进行 render，而要达到这个目标须要可能对渲染过程的工作进行暂停、终止以及复用，Fiber 便是利用数据结构实现了这样一个虚构堆栈帧。
这里不再对协调 (Reconciliation) 和调度 (Scheduling) 的具体过程，如 expirationTime 的权重设计、Effect lists 的 DFS 算法设计等进行讲述，有趣味的同学能够参看这篇文章(React Fiber 源码解析)
基于 React Hooks 波及到的 workInProgress，咱们重点看一下这里的设计
// This is used to create an alternate fiber to do work on.
export function createWorkInProgress(current: Fiber, pendingProps: any): Fiber {
let workInProgress = current.alternate;
if (workInProgress === null) {
// We use a double buffering pooling technique because we know that we'll
// only ever need at most two versions of a tree. We pool the "other" unused
// node that we're free to reuse. This is lazily created to avoid allocating
// extra objects for things that are never updated. It also allow us to
// reclaim the extra memory if needed.
workInProgress = createFiber(
current.tag,
pendingProps,
current.key,
current.mode,
);
workInProgress.elementType = current.elementType;
workInProgress.type = current.type;
workInProgress.stateNode = current.stateNode;
if (__DEV__) {
// DEV-only fields
workInProgress._debugID = current._debugID;
workInProgress._debugSource = current._debugSource;
workInProgress._debugOwner = current._debugOwner;
workInProgress._debugHookTypes = current._debugHookTypes;
}
workInProgress.alternate = current;
current.alternate = workInProgress;
} else {
workInProgress.pendingProps = pendingProps;
// Needed because Blocks store data on type.
workInProgress.type = current.type;
// We already have an alternate.
workInProgress.subtreeTag = NoSubtreeEffect;
workInProgress.deletions = null;
// The effect list is no longer valid.
workInProgress.nextEffect = null;
workInProgress.firstEffect = null;
workInProgress.lastEffect = null;
if (enableProfilerTimer) {
// We intentionally reset, rather than copy, actualDuration & actualStartTime.
// This prevents time from endlessly accumulating in new commits.
// This has the downside of resetting values for different priority renders,
// But works for yielding (the common case) and should support resuming.
workInProgress.actualDuration = 0;
workInProgress.actualStartTime = -1;
}
}
// Reset all effects except static ones.
// Static effects are not specific to a render.
workInProgress.effectTag = current.effectTag & StaticMask;
workInProgress.childLanes = current.childLanes;
workInProgress.lanes = current.lanes;
workInProgress.child = current.child;
workInProgress.memoizedProps = current.memoizedProps;
workInProgress.memoizedState = current.memoizedState;
workInProgress.updateQueue = current.updateQueue;
// Clone the dependencies object. This is mutated during the render phase, so
// it cannot be shared with the current fiber.
const currentDependencies = current.dependencies;
workInProgress.dependencies =
currentDependencies === null
? null
: {
lanes: currentDependencies.lanes,
firstContext: currentDependencies.firstContext,
};
// These will be overridden during the parent's reconciliation
workInProgress.sibling = current.sibling;
workInProgress.index = current.index;
workInProgress.ref = current.ref;
if (enableProfilerTimer) {
workInProgress.selfBaseDuration = current.selfBaseDuration;
workInProgress.treeBaseDuration = current.treeBaseDuration;
}
if (__DEV__) {
workInProgress._debugNeedsRemount = current._debugNeedsRemount;
switch (workInProgress.tag) {
case IndeterminateComponent:
case FunctionComponent:
case SimpleMemoComponent:
workInProgress.type = resolveFunctionForHotReloading(current.type);
break;
case ClassComponent:
workInProgress.type = resolveClassForHotReloading(current.type);
break;
case ForwardRef:
workInProgress.type = resolveForwardRefForHotReloading(current.type);
break;
default:
break;
}
}
return workInProgress;
}这里波及到的 workInProgress 和 current 两个树通过 alternate 这个指针的相互指引操作来实现首次渲染和非首次渲染的比照更新，保障两个队列都更新而不会失落，并且确保更新始终是 workInProgress 的一部分，这里还做了一个内存缓冲，奇次更新和偶次更新的循环复用
总结
通过学习 React16 对于 Fiber 源码及 React Hooks 的源码，咱们发现整个 React16 的底层外围是基于 Fiber 的优化与扩大，包含 dom-diff 的扩大等，相较于 Vue3 对于 Vue2 的更新，能够看出 React 的优化迭代思路更加充斥对计算机原理底层的思考与发现，当然这两个框架从出发点设计上也是有所不同，Vue 是基于组件级的优化，因此并不需要这样一个 Fiber 的数据结构去构建，但从真正的设计来看 Fiber 的架构设计思维形式的确更加合乎国外程序员的办法与韵味。(ps: 想要理解 Andrew Clark 介绍 Fiber 的同学，能够参看这篇文章 react-fiber-architecure)
参考
- Hook 简介
- 【第 2044 期】React Hooks 设计思维
- 【第 2037 期】React Hooks 实际指南
- ReactHooks 源码解析之 useEffect
- react hooks 源码剖析 — useState
- 分析 React Hooks 底层源码
- React Hook 的体系设计之一 – 分层
- React Hooks 的体系设计之二 – 状态粒度
- React Hooks 的体系设计之三 – 什么是 ref
- React Hooks 源码解析（译）
- [[译]深刻 React fiber 架构及源码](https://zhuanlan.zhihu.com/p/…
- React Fiber 源码解析