Populate

Populate starts with an explicit ref. Mongster does not infer relationships from naming conventions or separate relation metadata.

import { Post } from "./models";

const posts = await Post.find({}).populate("authorId", {
  select: ["name", "email"],
  excludeId: false,
});

console.log(posts[0].authorId);
                       
authorId: {
    name: string;
    email: string;
    _id: ObjectId;
} | null

Rules to remember

• The field must be declared as M.objectId().ref(() => Model).
• Populate currently works on top-level ref fields only.
• Array refs are not populatable yet.
• Nested populate paths are not supported.
• If the lookup does not match anything, Mongster normalizes the populated field back to null.

Select only what you need

Use select to limit fields from the populated document and excludeId when you want to omit _id from the populated payload.

ref() is terminal for now

At the moment, .ref() is the end of the chain. Do not add optional(), nullable(), default(), or defaultFn() after it.