Types for get() method of a reference?

[davidatsurge]

const RootStore = types.model({
  inbox: InboxStore,
  activeProject: types.maybeNull(
    types.reference(ProjectInbox, {
      get(identifier: string, parent /* HERE: What type do I use for `parent`? */) {
        return parent.inbox.projects.find(({ id }) => id == identifier) || null;
      },
      set(project) {
        return project.id;
      },
    })
  ),
});

If I set the type of parent to be Instance<typeof RootStore>, I get error: 'RootStore' implicitly has type 'any' because it does not have a type annotation and is referenced directly or indirectly in its own initializer..

PS: I am absolutely excited to have discovered this library.

[EmilTholin]

Hi @davidatsurge!

As you figured out TS sadly cannot figure out how to type RootStore if RootStore is used in its own definiton, so what you could do is type the parent.inbox to Instance<typeof InboxStore> instead to get around this.

Example

const RootStore = types.model({
  inbox: InboxStore,
  activeProject: types.maybeNull(
    types.reference(ProjectInbox, {
      get(identifier, parent) {
        if (parent === null) return null;

        const inbox = parent.inbox as Instance<typeof InboxStore>;

        return (
          inbox.projects.find(({ id }) => id === identifier) || (null as any)
        );
      },
      set(project) {
        return project.id;
      }
    })
  )
});

[davidatsurge]

Ahh, clever. Or at least I'm not that clever 😂. Thanks!