How do I limit the amount of document inside a schema in Sanity?

Question

I have a Schema called Blog and I only want there to be one Blog object and want to limit it to only one Blog object.

For example, Blog has an "Article". I don't want there to be multiple "Article" and want to put a limit to one article in a blog.

Answer 1

Are you trying to create a reference from an object of type "blog" to another of type "article"?

if so, this will do it:

{
  name: 'blog',
  type: 'object',
  fields: [
    {
      title: 'Article',
      name: 'article',
      type: 'reference',
      to: [{type: 'article'}]
    }
  ]
}

This will allow an editor to select only one "article" to reference to.

See the sanity docs for the reference field here: https://www.sanity.io/docs/reference-type

---

If instead you're trying to create a "singleton" document inside of Sanity Studio, one that an editor can't create more of, then this will do it:

// deskStructure.js
import S from '@sanity/desk-tool/structure-builder'

export default () =>
  S.list()
    .title('Base')
    .items([
      S.listItem()
        .title('Blog')
        .child(
          S.document()
            .schemaType('blog')
            .documentId('blog')
        ),
      ...S.documentTypeListItems().filter(listItem => !['blog'].includes(listItem.getId()))
    ])

Reference the guide in the Sanity docs: https://www.sanity.io/docs/create-a-link-to-a-single-edit-page-in-your-main-document-type-list