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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Implement `watch()` method for live query subscriptions","articleBody":"## Summary\nImplement a new `watch()` method on entity handlers to support live query subscriptions with filtering, sorting, and field selection.\n\n## Background\nCurrently, the SDK supports `subscribe()` for listening to all entity changes. We need to add support for filtered/query-based subscriptions that return snapshots of matching data.\n\n## Proposed API\n\n```typescript\ninterface QueryOptions {\n  filter?: Record\u003cstring, any\u003e;  // MongoDB-compatible filter\n  sort?: string;                  // Field name, prefix with '--' for descending\n  fields?: string[];              // Field selection\n}\n\ninterface SnapshotData\u003cT\u003e {\n  type: 'added' | 'modified' | 'removed';\n  entities: T[];\n}\n\n// New method on EntityHandler\nwatch(options: QueryOptions, callback: (snapshot: SnapshotData) =\u003e void): Subscription;\n```\n\n## Usage Example\n\n```typescript\nbase44.entities.Tasks.watch({\n  filter: { 'price': { '$gt': 10 } },\n  sort: '--price',\n  fields: ['id', 'price', 'name']\n}, (snapshot) =\u003e {\n  console.log(`Snapshot changed, reason: ${snapshot.type}`);\n  setTasks(snapshot.entities);\n});\n```\n\n## Implementation Details\n\n### Files to modify:\n- `src/modules/entities.ts` - Add `watch()` method to entity handler (similar pattern to existing `subscribe()` at line 166-188)\n- `src/modules/entities.types.ts` - Add `QueryOptions`, `SnapshotData`, and update `EntityHandler` interface\n- `src/utils/socket-utils.ts` - May need to extend room subscription to pass query options\n\n### Socket Integration:\n- Room naming convention: `entities:{appId}:{entityName}:watch` or similar\n- Need to emit query options when joining room\n- Handle `query_update` or similar event for snapshot updates\n\n### Key Considerations:\n- Initial fetch should happen immediately upon subscription\n- Return unsubscribe function (consistent with existing `subscribe()` pattern)\n- Handle reconnection with query re-subscription\n- JSON parse snapshot data from socket messages\n\n## Related\n- Depends on backend implementation of live query support\n- Design doc: Live Query Support implementation","author":{"url":"https://github.com/guyofeck","@type":"Person","name":"guyofeck"},"datePublished":"2026-01-22T19:48:34.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/83/javascript-sdk/issues/83"}