Fixing `Deprecated: React.Ref.setCurrent`

#reason #rescript #bucklescript

I keep finding myself having looking this up so I'm writing this note to myself.

Bad Code

This code throws a warning:

let useIsMounted = () => {
  let ref = React.useRef(false);

  React.useEffect0(() => {
    ref->React.Ref.setCurrent(true);
    Some(() => ref->React.Ref.setCurrent(false));
  });
  ref;
};

Warning

Warning 3: deprecated: React.Ref.setCurrent
Please directly assign to ref.current insteadocamllsp

The Fix

In ReasonML/Reason-React

let useIsMounted = () => {
  let ref = React.useRef(false);

  React.useEffect0(() => {
    ref.current = true;
    Some(() => ref.current = false);
  });
  ref;
};

In Rescript

let useIsMounted = () => {
  let ref = React.useRef(false)

  React.useEffect0(() => {
    ref.current = true
    Some(() => ref.current = false)
  })
  ref
}

Yes, they are the same except for the commas which the compiler will remove for you anyway.