database_skill

Overview

This skill provides best-practice patterns for persisting app data in Flutter: structured local SQL via Drift, lightweight typed preferences for small non-sensitive settings, and secure secret storage with flutter_secure_storage. It focuses on folder layout, DAO patterns, and small adapters that keep code testable and maintainable. The goal is safe, queryable caching and clear separation between sensitive and non-sensitive data.

How this skill works

Drift is used for centralized, queryable tables and feature-scoped DAOs that handle batch operations and transactions. SharedPreferences is wrapped in typed DAOs to expose strongly-typed entries and avoid direct global access. flutter_secure_storage is wrapped behind a small interface so secrets (tokens, credentials) are read/written via a mockable adapter for tests.

When to use it

• Use Drift for large lists, JSON blobs, offline cache, and any data you need to query or join.
• Use SharedPreferences for small, non-sensitive user settings and feature flags.
• Use flutter_secure_storage for tokens, credentials, and any sensitive secrets.
• Wrap platform APIs behind interfaces to enable mocking and unit testing.
• Prefer DAOs per feature to keep persistence logic localized and maintainable.

Best practices

• Place Drift tables centrally and DAOs in feature datasource folders for a feature-first layout.
• Perform cache replace operations in a single batch/transaction: delete old rows then insert new ones.
• Regenerate Drift code with the project’s build_runner command after schema changes.
• Never store secrets in SharedPreferences; always use secure storage for sensitive data.
• Expose typed preference entries (get/set) instead of passing SharedPreferences.getInstance around.

Example use cases

• Cache API responses as JSON rows in a Drift table with a cacheKey and timestamp, then read by cacheKey.
• Store a 'hasSeenOnboarding' boolean as a typed preference entry and access via .value/.setValue().
• Persist OAuth access and refresh tokens using a secure storage adapter implementing ISecureStorage.
• Replace cached search results by deleting entries for a cacheKey and inserting new JSON in one batch.
• Unit test token logic by injecting a mock ISecureStorage adapter instead of platform storage.