How to Use useRef with React Hook Form for File Inputs

Welcome back to my development notes!

Recently, I encountered a challenge while trying to integrate a useRef with a React Hook Form, specifically for an input of type file. The direct approach I initially attempted did not work as expected.

Consider a form structure like this:

 1const { register } = useFormContext();
 2const fileInputRef = useRef(null);
 3const handleClick = useCallback(() => {
 4  fileInputRef.current.click();
 5}, [fileInputRef]);
 6return (
 7  <>
 8    <input
 9      type="file"
10      ref={fileInputRef}
11      {...register("file")}
12    />
13    <button onClick={handleClick}>Upload</button>
14  </>
15);

In this scenario, fileInputRef remained null within the handleClick function, preventing the desired interaction. After some research, I discovered that the register method from React Hook Form needs to be handled differently when combining it with a useRef.

The correct approach involves destructuring the ref property from the register method’s return value and then assigning both the useRef and the register’s ref to the input element. Here’s the corrected implementation:

 1const { register } = useFormContext();
 2const { ref, ...inputProps } = register("file");
 3const fileInputRef = useRef(null);
 4const handleClick = useCallback(() => {
 5  fileInputRef.current.click();
 6}, [fileInputRef]);
 7
 8return (
 9  <>
10    <input
11      type="file"
12      ref={(e) => {
13        fileInputRef.current = e;
14        ref(e);
15      }}
16      {...inputProps}
17    />
18    <button onClick={handleClick}>Upload</button>
19  </>
20);

By passing a function to the ref prop of the input element, we can ensure that both fileInputRef.current and React Hook Form’s internal ref are correctly assigned.

I hope this solution proves helpful if you face similar issues with refs and React Hook Form.

Note: This is a development note, not a comprehensive tutorial. For more in-depth information on React Hook Form, please refer to the official documentation.