AtCollection.exists

AtCollection.exists will check if a collection item exists cheaply

AtCollection.exists

Just like AtCollection.get, the mandatory fields to use AtCollection.exists are both id and owner.

import 'package:at_client/at_client.dart';

final bool there = await todos.exists('daily-standup', todos.self);

Checking items shared with you

The code sample below shows how to check if someone like @bob shared data with you under the daily-standup id and the corresponding AtCollection namespace.

final bool bob =
    await todos.exists('daily-standup', '@bob'.toAtsign());

For items owned by someone else, exists probes your local cached: copy. So exists and getOrNull(id, owner) != null always agree, including while offline.

How is this cheaper than AtCollection.getOrNull

For your own items, exists short-circuits against an in-process cache of ids you've already written or read. This skips json decodes and round trips. For items owned by others it still avoids the decode step and checks whether the key is present, not whether the value parses.

Use getOrNull when you need the item itself. Use exists when you only need to know if it's there or not.