useFormikSlice feature that updates when I need

[outerlook]

🚀 Feature request

Current Behavior

Currently, when I need to access some form's values from deep nested components, if they are many, I use useFormikContext(), but it then gets updated and re rendered on every change to formik context (right?).

If I need to optmize this, I start using many useField()`s which already updates only if the value updates. But then it gets ugly quickly.

Desired Behavior

I would like some function which returns:

• values (the ones I need)
• errors (here too)
• setFieldValue (could this remain typed to work with all fields or should be only the one I need?)
• setFieldErrors
  ... useful things already present on useField but in a batch way.

Suggested Solution

Sort of useFormikSlice([field1, field2, field3]) maybe?

Types would be like
useFormikSlice< AllMyValues >([field1,field2,field3])
that returns things with Pick< AllMyValues, field1|field2|field3>

Who does this impact? Who is this for?

People aiming to optimize some uses with less code.

Describe alternatives you've considered

should keep things simple and just add an overload to useFormikContext() which accepts one arg "deps"?

Additional context

Sorry if this behaviour already exists somehow and I did not realize 😁

[jaredpalmer]

Yeah would be rad, but there isn’t a way to do this with hooks (only components using scu). This is because there is no way to subscribe to slices of context with hooks right now. To make a hook like this we would have to rewrite formik so that state would live outside of react and in an external pub/sub object.

I’ve considered this multiple times but have punted, hoping that react team would add this functionality to useContext, but I doubt that will happen at this point. Even though this goes against my initial design principles of formik, they were formed before hooks existed, when sCU was viable.

I think it’s worth experimenting with pub sub, but in the short term it would be rather simple to add <FormikSlice/> and withFormikSlice(). Or we could pass connect() mapFormikStateAndHelpersToProps like fn