Ts forwardRef与useImperativeHandle 父类调用子类的方法

export interface RChild{
  input:()=>void
  ...
}
export interface TChild{
  setIndex:(key)=>void
}
const mapStateToProps=({nav})=>({index:nav.index})
const mapDispathToProps={
  setIndex:(key)=>({
    type:'nav/setIndex',
    payload:key
    })
}
const child=forwardRef<RChild,TChild>({setIndex},ref}=>{
  useImperativeHandle(ref,()=>({
    input,   //传给父类的方法或者值
  })
  return (<>.....</>)
})
export defualt child
//注意
//如果child组件需要是基于connect的话，父类可以获取不到子类方法，界面也可能警告attempts to access this ref
export defualt connect(mapStateToProps,mapDispathToProps,null,{forwardRef:true})(child)

const Parent =()=>{
  const preRef=useRef<RChild>(null)
     // 调用input方法时；
  //preRef.current!.input()
  return (<>
    <Child ref={preRef}/>
        </>)
}
export defualt Parent