useContext 是 React 中的一个 Hooks，它用于访问 React 上下文（Context），并允许您在函数组件中共享...
is called in function that is neither a React function component nor a custom React Hook function...
SomeContext具有InitialStateInterface类型，该类型将handleSettingFooBar定义为handleSettingFooBar: Function，...
Here is the full example using React Context: import { useState, createContext, useContext } from "react"; import ReactDOM from "react-dom/client"; const UserContext = createContext(); function Component1() { const [user, setUser] = useState("Jesse Hall"); return ( <UserContext.Provider...
Provider value={cnt}>{children}</ValueCtx.Provider> } function CompA({}) { const cnt = useContext(ValueCtx) // 组件内使用 cnt return <div>组件 CompA Render 次数:{renderOnce("CompA")}</div> } function CompB({}) { const cnt = useContext(ValueCtx) // 组件内使用 cnt return <div>...
In a class component, using React Context can be slightly different. The useContext hook is not available for class components, but you can still use the contextType property to associate a context with a class component. Once the contextType is set, you can access the context data using ...
子组件使用useContext导致的重渲染 // value是个复杂类型的对象,父组件的重渲染会导致重新生成{mode}constThemeContext=React.createContext<Theme>({mode:'light'}); const useTheme = () =>{returnuseContext(ThemeContext);}; // before: // 父组件 ...
下面是useContext在类型声明文件中的定义: functionuseContext<T>(context: Context<T>/*, (not public API) observedBits?: number|boolean*/): T;/** * Returns a stateful value, and a function to update it. * * @version 16.8.0 * @see https://reactjs.org/docs/hooks-reference.html#usestate...
useContext只可以用在函数组件中或者自定义hook,且第二个参数不会覆盖第一个 大致原理 ReactContext.js 中的createContext // createContext 创建一个Context ,即入口函数exportfunctioncreateContext<T>( defaultValue: T, calculateChangedBits: ?(a: T, b: T) => number, ...
exportdefaultfunctionDetails() { const { user }=useContext(UserContext);return(<div>详细信息: {`${user.email} ${user.phone}`}</div>); } 这有一个问题,Header中setUser时,App所有子组件都会重新渲染,能不能只渲染consumer组件?要使用children属性,children是一个特殊的属性,<A><B/> </A>,A组件...