Today I Learned

A Hashrocket project

No-op reducer in Reason React

Generally in ReasonReact if you have a reducer component that component will have a reducer function that looks like this:

reducer: (action, state) => {
    switch(action) {
    | Change(newValue) =>
        ReasonReact.Update({value: newValue})
  }
}

ReasonReact.Update is a variant that constructs with a state value.

Another variant you can return from the reducer function is ReasonReact.NoUpdate, allowing you to not update the state if circumstances do not warrant it.

reducer: (action, state) => {
    switch(action) {
    | Change("UghWat") =>
        ReasonReact.NoUpdate
    | Change(newValue) =>
        ReasonReact.Update({value: newValue})
  }
}

Not if the user enters “UghWat” we won’t update the state with that useless value.