How to update a hidden field programmatically when updating a document in Sanity.io.

Afternoon, does anyone know if there’s some way I can update some data programmatically when updating a document? e.g I’d like to update a

readingTime

hidden field when a user saves a blog post based on the text content in said blog post. Cheers!

This might be of help - https://www.sanity.io/plugins/sanity-plugin-computed-field

Thanks, User. Unfortunately this doesn't seem to be able to be used with GraphQL. I was hoping for some kind of

onAfterUpdate

callback in the schema or something.

Hum. I guess you could create a webhook to write a patch to the dataset whenever the relevant document is published?
However, this seems quite roundabout to me, since if you want to compute the readingTime for a field you could do it
directly in GROQ .
You could additionally have a field in the editor in case you want to override it as well.

Yeah, that's a bit convoluted for the use-case.

You could use a custom input component or a document action. For a custom input, you could use

renderDefault

so that you don’t actually have to reimplement the component or logic of the field, but use something like a

useEffect

to write to your hidden field. It would likely write on every keystroke and may impact performance within the Studio. If you use a document action, you can replace the default Publish action so that it updates the field, then completes the action .

Ah, document action would possibly be a goer. Would be good if actions could be run against the normal publish action.