react useContext() 性能,自定义钩子内的 useContext

IT技术 javascript reactjs rendering react-hooks react-context
2021-05-06 10:37:08

我使用了一个使用React Hooks的结构它基于包含减速器组合的全局上下文(如在 Redux 中)。此外,我广泛使用自定义钩子来分离逻辑。我有一个包含异步 API 请求的钩子,它变得非常麻烦,我有机会将这个钩子的几乎每个函数拆分成其他钩子,但是这些函数中的每一个都使用全局上下文(更准确地说 - 从 useReducer() 调度) )。

所以,问题:

  1. 可以在每个需要它的钩子中使用 useContext() 吗?
  2. 例如,如果我创建 10 个在内部使用 useContext() 并在组件中使用它们的自定义钩子,它将如何影响性能。

例子:

供应商/Store.js

import React, { createContext, useReducer } from 'react';

export const StoreContext = createContext();

export const StoreProvider = ({ children }) => {
  /**
   * Store that contains combined reducers.
   */
  const store = useReducer(rootReducer, initialState);

  return (
    <StoreContext.Provider value={store}>{children}</StoreContext.Provider>
  );
};

钩子/useStore.js

import { useContext } from 'react';
import { StoreContext } from '../providers';

export const useStore = () => useContext(StoreContext);

钩子/useFoo.js

import { useCallback } from 'react';
import { useStore } from './useStore';

export const useFoo = () => {
  const [, dispatch] = useStore();

  const doFoo = useCallback(
    async params => {
      dispatch(actions.request());

      try {
        const res = await SomeService.getSomething(params);
        dispatch(actions.add(res));
        dispatch(actions.success());
      } catch (error) {
        dispatch(actions.failure());
      }
    },
    [dispatch]
  );

  return { doFoo };
};

钩子/useBar.js

import { useCallback } from 'react';
import { useStore } from './useStore';

export const useBar = () => {
  const [, dispatch] = useStore();

  const doBar = useCallback(
    async params => {
      dispatch(actions.request());

      try {
        const res = await SomeService.getSomething(params);
        dispatch(actions.success());
        dispatch(actions.add(res));
      } catch (error) {
        dispatch(actions.failure());
      }
    },
    [dispatch]
  );

  return { doBar };
};

钩子/useNext.js

...
import { useStore } from './useStore';

export const useNext = () => {
  const [, dispatch] = useStore();

  ...
};

组件/SomeComponent.js

const SomeComponent = () => {
  // use context
  const [store, dispatch] = useStore();

  // and here is the context
  const { doFoo } = useFoo();

  // and here
  const { doBar } = useBar();

  // and here
  useNext();

  return (
    <>
      <Button onClick={doFoo}>Foo</Button>
      <Button onClick={doBar}>Bar</Button>
      // the flag is also available in another component
      {store.isLoading && <Spin />}
    </>
  )
}
1个回答

在内部,钩子可以引用组件拥有的状态队列。在 React 钩子系统的幕后 - Eytan Manor

useContext只是从相关的上下文提供者引用全局状态。useContext正如您所关心的,几乎没有开销