Subcollections

Declare a subcollection

Add a @Collection whose path uses * for each parent document ID:

@Schema()
@Collection<User>('users')
@Collection<Post>('users/*/posts')
@Collection<Comment>('users/*/posts/*/comments')
const appSchema = AppSchema();

Access a subcollection

Each subcollection gets a method on the ODM. Its name joins the path's collection names, and it takes one argument per *, in path order:

Path	Accessor
users/*/posts	odm.usersPosts(userId)
users/*/posts/*/comments	odm.usersPostsComments(userId, postId)

final janePosts = odm.usersPosts('jane');

// Everything a root collection offers works here
await janePosts.set(post);
final hello = await janePosts('hello-world').get();
final recent = await janePosts
    .orderBy(($) => ($.createdAt(descending: true),))
    .limit(10)
    .get();

final comments = odm.usersPostsComments('jane', 'hello-world');
final count = await comments.count();

Subcollections also work in batches and transactions:

await odm.runBatch((batch) {
  odm.usersPosts('jane').inBatch(batch).delete('draft');
});

One model, many collections

The same model can be used in any number of collections, for example Post in both posts and users/*/posts. Its generated code exists once.

Notes

• Always pass every parent ID. Passing null or leaving an argument out targets a path that contains the text null.
• Deleting a parent document does not delete its subcollections.
• Queries across all subcollections with the same name (collection group queries) are not available through the ODM. Use odm.firestore.collectionGroup('posts') from cloud_firestore for those.