反应钩子 useRef 不适用于样式组件和 typescript

Question

I've some problem using the useRef hook with a styled component.

Linter alerts me that Object is possibly 'null' inside the didMount useEffect . Any idea about this?

This is not a duplicate for 2 reason:

• The old answer refers to the ref used in a class component, that was the only way to use it before React hooks,
• The innerRef props isn't supported anymore in the current version of styled components.

Here's a sample snippet of my component:

import React, { useRef, useEffect } from 'react';
import styled from 'styled-components';

const StyledInput = styled.input`
  background: transparent;
`

const MyForm = () => {
  const inputRef = useRef(null);
  
  useEffect(() => {
    if (inputRef && inputRef.current) {
      inputRef.current.focus(); //Object is possibly 'null'
    }
  }, []);

  return (
    <StyledInput ref={inputRef}/>
  );
}

Answer 1

I've finally found a solution:

const inputRef = useRef() as React.MutableRefObject<HTMLInputElement>;

---

It works for me:

import React, { useRef, useEffect } from 'react';
import styled from 'styled-components';

const StyledInput = styled.input`
  background: transparent;
`

const MyForm = () => {
  const inputRef = useRef() as React.MutableRefObject<HTMLInputElement>;

  useEffect(() => {
    if (inputRef && inputRef.current) {
      inputRef.current.focus();
    }
  }, []);

  return (
    <StyledInput ref={inputRef}/>
  );
}

Answer 2

As an alternative to the current accepted answer, you can also do:

const inputRef = useRef<HTMLInputElement>(null);

Answer 3

Pass your inputRef in the array argument of useEffect and let's see if that works, you aren't guaranteed to have a .current in your ref, so you should run the effect every time inputRef changes