如何更新 Recoil.js 外部组件中的原子（状态）？ （反应）

Posted 2023-03-07

【中文标题】如何更新 Recoil.js 外部组件中的原子（状态）？ （反应）

【英文标题】：How to update atoms (state) in Recoil.js outside components ? (React)

【发布时间】：2021-10-26 22:20:35

【问题描述】：

我是 Recoil.js 的新手，我在应用中为登录用户提供了以下原子和选择器：

const signedInUserAtom = atom<SignedInUser | null>(
    key: 'signedInUserAtom',
    default: null
)

export const signedInUserSelector = selector<SignedInUser | null>(
    key: 'signedInUserSelector',
    get: ( get ) => get(signedInUserAtom),
    set: ( set, get , newUserValue) => 
        // ... Do a bunch of stuff when a user signs in ...

        set(signedInUserAtom, newUserValue)
    
)

所以基本上我使用signedInUserSelector 来设置新用户。 现在，我想要一些函数通过选择器设置用户，并在我的组件中使用它们，例如：

  export async function signInWithGoogleAccount() 
     const googleUser = async googleClient.signIn()
     // here I need to set the user atom like:
     //  const [user, setUser] = useRecoilState(signedInUserSelector)
     // setUser(googleUser)
  

  export async function signInWithLocalAccount(email: string, password: string) 
     const localUser = async localClient.signIn(email, password)
     // here I need to set the user atom like:
     //  const [user, setUser] = useRecoilState(signedInUserSelector)
     // setUser(localUser)
  

  export async function signOut() 
      await localClient.signOut()
      // here I need to set the user atom like:
     //  const [user, setUser] = useRecoilState(signedInUserSelector)
     // setUser(null)
  

问题是因为这些函数没有在组件内部定义，所以我不能使用反冲钩子（比如useRecoilState 来访问选择器/原子）。

最后我希望有任何组件能够做到：

function SignInFormComponent() 
  return <button onClick=signInWithGoogleAccount>Sign In</button>

但是如果signInWithGoogleAccount 中的选择器/原子不在组件中，我该如何访问它？

【参考方案1】：

我认为唯一的方法（至少在几个月前）是一种 hack，您可以在其中包含一个非渲染组件，该组件使用反冲钩子并从中导出提供的函数。

见：https://github.com/facebookexperimental/Recoil/issues/289#issuecomment-777249693

下面是我自己的项目中实现这一点的文件，主要基于上面的链接。您只需将<RecoilExternalStatePortal /> 放在您的应用程序树中保证始终呈现的任何位置。

这似乎是 Recoil API 中的一个遗漏，恕我直言。

import React from 'react'
import  Loadable, RecoilState, RecoilValue, useRecoilCallback, useRecoilTransactionObserver_UNSTABLE  from 'recoil'

/**
 * Returns a Recoil state value, from anywhere in the app.
 *
 * Can be used outside of the React tree (outside a React component), such as in utility scripts, etc.

 * <RecoilExternalStatePortal> must have been previously loaded in the React tree, or it won't work.
 * Initialized as a dummy function "() => null", it's reference is updated to a proper Recoil state mutator when RecoilExternalStatePortal is loaded.
 *
 * @example const lastCreatedUser = getRecoilExternal(lastCreatedUserState);
 */
export function getRecoilState<T>(recoilValue: RecoilValue<T>): T 
  return getRecoilLoadable(recoilValue).getValue()


/** The `getLoadable` function from recoil. This shouldn't be used directly. */
let getRecoilLoadable: <T>(recoilValue: RecoilValue<T>) => Loadable<T> = () => null as any

/**
 * Sets a Recoil state value, from anywhere in the app.
 *
 * Can be used outside of the React tree (outside a React component), such as in utility scripts, etc.
 *
 * <RecoilExternalStatePortal> must have been previously loaded in the React tree, or it won't work.
 * Initialized as a dummy function "() => null", it's reference is updated to a proper Recoil state mutator when RecoilExternalStatePortal is loaded.
 *
 * @example setRecoilExternalState(lastCreatedUserState, newUser)
 */
export let setRecoilState: <T>(recoilState: RecoilState<T>, valOrUpdater: ((currVal: T) => T) | T) => void = () =>
  null as any

/**
 * Utility component allowing to use the Recoil state outside of a React component.
 *
 * It must be loaded in the _app file, inside the <RecoilRoot> component.
 * Once it's been loaded in the React tree, it allows using setRecoilExternalState and getRecoilExternalLoadable from anywhere in the app.
 *
 * @see https://github.com/facebookexperimental/Recoil/issues/289#issuecomment-777300212
 * @see https://github.com/facebookexperimental/Recoil/issues/289#issuecomment-777305884
 * @see https://recoiljs.org/docs/api-reference/core/Loadable/
 */
export function RecoilExternalStatePortal() 
  // We need to update the getRecoilExternalLoadable every time there's a new snapshot
  // Otherwise we will load old values from when the component was mounted
  useRecoilTransactionObserver_UNSTABLE(( snapshot ) => 
    getRecoilLoadable = snapshot.getLoadable
  )

  // We only need to assign setRecoilExternalState once because it's not temporally dependent like "get" is
  useRecoilCallback(( set ) => 
    setRecoilState = set

    return async () => 
      // no-op
    
  )()

  return <></>

【参考方案2】：

正如我在another answer 中指出的那样，您通常不想遇到这种情况，但是如果您最终确实需要更新 React 之外的原子组件，您可以尝试@ 987654322@.

在您拥有 RecoilRoot 的同一个文件中，您将拥有类似的内容：

import React from 'react';
import  RecoilRoot  from "recoil"
import RecoilNexus from 'recoil-nexus'

export default function App() 
  return (
    <RecoilRoot>
      <RecoilNexus/>
      
      /* ... */
      
    </RecoilRoot>
  );
;


export default App;

然后，无论您需要在哪里读取/更新值：

import yourAtom from './yourAtom'
import  getRecoil, setRecoil  from 'recoil-nexus'

最终你可以像这样获取和设置值：

const loading = getRecoil(loadingState)

setRecoil(loadingState, !loading)

就是这样！

免责声明：我是图书馆的作者。

---

查看此CodeSandbox 以获取实时示例。

【讨论】：

老兄，太棒了，你救了我的一天