Could useField take a defaultValue?

[aaronadamsCA]

We have a lot of fieldsets that get reused between "new" forms and "edit" forms:

• In "new" forms, fields might need some initial value, like "this box should be checked by default".
• In "edit" forms, the default value instead comes from the server.

What I'd love is some way to set these initial values at the fieldset level, to be used only if the form has no defaultValue.

My idea was a defaultValue option on the useField hook:

• If useForm was called with defaultValue === undefined, then useField would use its defaultValue.
• If useForm was called with defaultValue !== undefined, then useField would ignore its defaultValue.

I wouldn't want or expect anything more complex than this—definitely no merging of values. This would be super simple; the defaultValue passed to useField would apply if and only if no defaultValue was passed to useForm.

I don't know if this suggested API is the best one, but I think this very common use case would be great (and hopefully straightforward) to support. What we're doing right now is adding a defaultValue property to each fieldset, then manually adding it to the defaultValue passed to useForm; the problem with this, of course, is that it's easy to forget.

Thanks!

[aust1nz]

The way I've seen this done in this and other form-helper libraries is with a function you'd pass to defaultValue.

const [form, fields] = useForm({
  defaultValue: (user?: UserSchema) => ({
    id: user?.id ?? '',
    address: {
      street: user?.address.street ?? '',
      isPublic: user?.address.street ?? true
    }
  })
});

I haven't tested it, but I think that'll mean that your useField hooks will inherit whatever value you set up in the useForm hook. Does that solve your issue?

[aaronadamsCA]

I don't think so, because it still requires us to "hoist" default values up to the form component.

In our case we export a defaultValue from the fieldset component (if there is one), and then the form component passes it to useForm. But if you forget to do this, a type check won't save you. It's an implementation detail of the fieldset I'd prefer to be able to hide from the form.