AgentSkillsCN

iOS Persistence

在 SwiftData、Core Data 以及本地存储方面的规范。

SKILL.md
--- frontmatter
name: iOS Persistence
description: Standards for SwiftData, Core Data, and Local Storage.
metadata:
  labels: [ios, persistence, swiftdata, coredata, sqlite]
  triggers:
    files: ['**/*.xcdatamodeld', '**/*Model.swift']
    keywords:
      [
        PersistentContainer,
        FetchRequest,
        ManagedObject,
        Query,
        ModelContainer,
        Repository,
      ]

iOS Persistence Standards

Priority: P0

Implementation Guidelines

SwiftData (iOS 17+)

  • •Models: Use @Model macro for pure Swift classes.
  • •Container: Use ModelContainer for schema management. Inject into the environment for SwiftUI apps.
  • •Queries: Use @Query for declarative data fetching in Views.

Core Data (Standard)

  • •Persistent Stack: Initialize NSPersistentContainer in a dedicated PersistenceController.
  • •Context Management: Use viewContext for UI tasks and newBackgroundContext() for heavy imports to avoid blocking the main thread.
  • •FetchedResultsController: Use NSFetchedResultsController for efficient list management with change tracking.

Best Practices

  • •Migration: Always perform lightweight migrations for minor schema changes. Use versioned models for complex migrations.
  • •Threading: Managed objects are not thread-safe. Always access them on the context's queue (e.g., perform { ... }).
  • •Batching: Use NSBatchUpdateRequest or NSBatchDeleteRequest for large datasets.

Anti-Patterns

  • •Main Thread Blocking: **No heavy I/O on ViewContext**: Use private background contexts.
  • •Manual String Keys: **No string-based predicates**: Use KeyPaths or generated helpers.
  • •Missing Merge Policies: **No merge strategy**: Explicitly set mergePolicy (e.g., mergeByPropertyObjectTrump).

References