引用传递（Ref forwading）是一种通过组件向子组件自动传递 引用ref 的技术。对于应用者的大多数组件来说没什么作用。但是对于有些重复使用的组件，可能有用。例如某些input组件，需要控制其focus，本来是可以使用ref来控制，但是因为该input已被包裹在组件中，这时就需要使用Ref forward来透过组件获得该input的引用。

作者：pipu
链接：https://www.jianshu.com/p/fac884647720/
来源：简书
简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。

1. 学习资料

JS-react forward ref高阶组件透传-1
JS-react forward ref高阶组件透传-2
TS-react forward ref高阶组件透传

2. 普通input透传

2.1 TS版本

Parent.tsx

import React, { useRef, useState } from 'react'
import Child from './Child';export default function Parent() {const inputRef = useRef<HTMLInputElement>(null);const [text,setText] = useState<string>('');return (<div><button onClick={()=>{inputRef.current?.focus();setText('');}}>父组件内按钮-点击input获取焦点并清空value</button><Child ref={inputRef} text={text} changeVal={(val:string)=>{setText(val);}}></Child></div>)
}

Child.tsx

import React, { ChangeEvent, forwardRef, MutableRefObject, useCallback, useRef } from 'react'interface Iprops {text:string;changeVal:Function
}const Child = forwardRef<HTMLInputElement,Iprops>((props,ref) => {
const localRef = useRef<HTMLInputElement | null>(null);const onChange = useCallback((e:ChangeEvent<HTMLInputElement>)=>{props.changeVal(e.target.value)
},[props]);return (<div><input type="text" value={props.text} ref={el=>{localRef.current = el;console.log(ref)if (typeof ref === 'function') {ref(el);} else if (ref) {(ref as MutableRefObject<HTMLInputElement>).current = el!;}}} onChange={onChange}/><button onClick={()=>{console.log(localRef.current)console.log(localRef.current?.value)console.log(props.text)}}>子组件内按钮-点击获取input输入值</button></div>
)
}) export default Child

2.2 JS版本

Child.tsx

import React, { forwardRef, useCallback} from 'react'
const Child = forwardRef((props,ref) => {const onChange = useCallback((e)=>{props.changeVal(e.target.value)},[props]);return (<div><input type="text" value={props.text} ref={ref} onChange={onChange}/><button onClick={()=>{console.log(ref.current)console.log(ref.current.value)console.log(props.text)}}>子组件内按钮-点击获取input输入值</button></div>)
}) export default Child

3. TS-Antd-Form组价透传

Parent.tsx

import React, { useRef } from 'react'
import type { FormInstance } from 'antd/es/form';
import Child from './Child';export default function Parent() {const addForm = useRef<FormInstance>(null);const updateForm= useRef<FormInstance>(null);return (<div><button onClick={()=>{addForm.current?.validateFields().then((values) => {console.log(values);}).catch((err) => {console.log(err);});}}>父组件内按钮-点击input获取焦点并清空value</button><UserForm ref={addForm} regionList={regionList} roleList={roleList} /><UserForm ref={updateForm} regionList={regionList} roleList={roleList} /></div>)
}

Child.tsx

import React, { forwardRef, MutableRefObject, Ref, useEffect} from "react";
import { Form } from "antd";
import type { FormInstance } from 'antd/es/form';interface UserFormProps {isUpdateRegionDisabled?:boolean;regionList:any[];roleList:any[];
}
const assignRefs = <T extends unknown>(...refs: Ref<T | null>[]) => {return (node: T | null) => {refs.forEach((r) => {if (typeof r === "function") {r(node);} else if (r) {(r as MutableRefObject<T | null>).current = node;}});};
};const UserForm = forwardRef<FormInstance,UserFormProps>((props,ref)=>{const localRef = React.useRef<FormInstance | null>(null);useEffect(() => {console.log('localRef',localRef.current)}, [props]);return (<Form layout="vertical" ref={assignRefs(localRef, ref)}></Form>)
})