How do I install the Core Data skill?

Run npx skillmds@latest add caglarbaranbora/core-data in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

What does the Core Data skill do?

Route Core Data implementation tasks to the correct Knowledge Contracts -- subclassing NSManagedObject and choosing an .xcdatamodeld Codegen mode (Class Definition/Manual-None/Category+Extension) with @NSManaged properties, standing up NSPersistentContainer via loadPersistentStores(completionHandler:) and viewContext with NSPersistentStoreDescription store options, NSManagedObjectContext CRUD (insertNewObject(forEntityName:into:)/init(context:), delete(_:), save(), perform(_:)/performAndWait(_:), parent), fetching with NSFetchRequest /NSPredicate/NSSortDescriptor/context.fetch(_:)/@FetchRequest, and NSDeleteRule referential integrity. Use when writing @NSManaged public var, NSEntityDescription.insertNewObject(forEntityName:into:), Task(context:), NSPersistentContainer(name:), container.loadPersistentStores { }, container.viewContext, NSPersistentStoreDescription, context.insert(_:)/delete(_:)/save(), context.perform { }/performAndWait { }, context.parent, NSFetchRequest (entityName:), NSPredicate(forma It is listed under Productivity on SkillMD.

Is Core Data safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Core Data?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Core Data free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Core Data?

caglarbaranbora (@caglarbaranbora) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Core Data by caglarbaranbora — Agent Skill

Name: Core Data
Author: caglarbaranbora

Core Data

Route Core Data implementation tasks to the correct Knowledge Contracts -- subclassing NSManagedObject and choosing an .xcdatamodeld Codegen mode (Class Definition/Manual-None/Category+Extension) with @NSManaged properties, standing up NSPersistentContainer via loadPersistentStores(completionHandler:) and viewContext with NSPersistentStoreDescription store options, NSManagedObjectContext CRUD (insertNewObject(forEntityName:into:)/init(context:), delete(_:), save(), perform(_:)/performAndWait(_:), parent), fetching with NSFetchRequest<T>/NSPredicate/NSSortDescriptor/context.fetch(_:)/@FetchRequest, and NSDeleteRule referential integrity. Use when writing @NSManaged public var, NSEntityDescription.insertNewObject(forEntityName:into:), Task(context:), NSPersistentContainer(name:), container.loadPersistentStores { }, container.viewContext, NSPersistentStoreDescription, context.insert(_:)/delete(_:)/save(), context.perform { }/performAndWait { }, context.parent, NSFetchRequest<Item>(entityName:), NSPredicate(forma

File contents

Core Data — Foundations Skill

Purpose

Route Core Data implementation tasks to the minimum required Core Data Knowledge Contracts. v1 scope is subclassing NSManagedObject and choosing an .xcdatamodeld Codegen mode with @NSManaged properties, standing up and loading an NSPersistentContainer, performing CRUD through an NSManagedObjectContext with basic thread confinement and a basic parent-child context relationship, fetching with NSFetchRequest/ @FetchRequest, and NSDeleteRule/inverse-relationship referential integrity -- not CloudKit sync, not migration, not NSFetchedResultsController, not advanced multi-context concurrency, and not SwiftData interop.

Routing

Load only the contracts relevant to the task. All paths relative to knowledge/core-data/.

Subclassing NSManagedObject; choosing a Codegen mode (Class Definition/Category+Extension/Manual-None); declaring @NSManaged attribute or relationship properties; or asking what Xcode's generated code does and doesn't synthesize -> model-definition.md
Constructing NSPersistentContainer(name:); calling loadPersistentStores(completionHandler:) and handling its error; reading viewContext; configuring a store via NSPersistentStoreDescription/persistentStoreDescriptions; or injecting a context with .environment(\.managedObjectContext, ...) -> persistent-container-setup.md
Inserting via NSEntityDescription.insertNewObject(forEntityName:into:) or a generated init(context:); calling delete(_:)/save(); checking hasChanges; wrapping work in perform(_:)/ performAndWait(_:); or setting up a basic parent-child context via parent -> managed-object-context-crud.md
Building an NSFetchRequest<T> with a predicate/sortDescriptors; calling context.fetch(_:); or declaring @FetchRequest in a SwiftUI view -> fetching-with-nsfetchrequest.md
Choosing an NSDeleteRule value (.cascadeDeleteRule/ .nullifyDeleteRule/.denyDeleteRule/.noActionDeleteRule); reasoning about what happens to related objects on delete; or diagnosing a relationship missing its inverseRelationship -> relationships-and-delete-rules.md

Never load more than the contracts relevant to the specific question.

Stop Conditions

Stop and report if the requested topic has no matching Knowledge Contract in knowledge/core-data/ — do not guess or fall back to general knowledge.

NSPersistentCloudKitContainer/CloudKit sync — Deferred
Lightweight and mapping-model migration (NSMigrationManager, versioned/mapping models) — Deferred
NSFetchedResultsController — Deferred; do not fabricate its behavior from fetching-with-nsfetchrequest
Multi-context concurrency beyond one parent-child relationship — Deferred
SwiftData interop or migration (@Model, ModelContainer, ModelContext) — owned by swiftdata; do not answer SwiftData questions from Core Data contracts or fabricate a shared API surface

---name: core-datadescription: Route Core Data implementation tasks to the correct Knowledge Contracts -- subclassing NSManagedObject and choosing an .xcdatamodeld Codegen mode (Class Definition/Manual-None/Category+Extension) with @NSManaged properties, standing up NSPersistentContainer via loadPersistentStores(completionHandler:) and viewContext with NSPersistentStoreDescription store options, NSManagedObjectContext CRUD (insertNewObject(forEntityName:into:)/init(context:), delete(_:), save(), perform(_:)/performAndWait(_:), parent), fetching with NSFetchRequest<T>/NSPredicate/NSSortDescriptor/context.fetch(_:)/@FetchRequest, and NSDeleteRule referential integrity. Use when writing @NSManaged public var, NSEntityDescription.insertNewObject(forEntityName:into:), Task(context:), NSPersistentContainer(name:), container.loadPersistentStores { }, container.viewContext, NSPersistentStoreDescription, context.insert(_:)/delete(_:)/save(), context.perform { }/performAndWait { }, context.parent, NSFetchRequest<Item>(entityName:), NSPredicate(forma---# Core Data — Foundations Skill## PurposeRoute Core Data implementation tasks to the minimum required Core DataKnowledge Contracts. v1 scope is subclassing `NSManagedObject` and choosingan `.xcdatamodeld` Codegen mode with `@NSManaged` properties, standing upand loading an `NSPersistentContainer`, performing CRUD through an`NSManagedObjectContext` with basic thread confinement and a basicparent-child context relationship, fetching with `NSFetchRequest`/`@FetchRequest`, and `NSDeleteRule`/inverse-relationship referentialintegrity -- not CloudKit sync, not migration, not`NSFetchedResultsController`, not advanced multi-context concurrency, andnot SwiftData interop.## RoutingLoad only the contracts relevant to the task. All paths relative toknowledge/core-data/.- Subclassing `NSManagedObject`; choosing a Codegen mode (Class Definition/Category+Extension/Manual-None); declaring `@NSManaged` attribute or relationship properties; or asking what Xcode's generated code does and doesn't synthesize -> model-definition.md- Constructing `NSPersistentContainer(name:)`; calling `loadPersistentStores(completionHandler:)` and handling its error; reading `viewContext`; configuring a store via `NSPersistentStoreDescription`/`persistentStoreDescriptions`; or injecting a context with `.environment(\.managedObjectContext, ...)` -> persistent-container-setup.md- Inserting via `NSEntityDescription.insertNewObject(forEntityName:into:)` or a generated `init(context:)`; calling `delete(_:)`/`save()`; checking `hasChanges`; wrapping work in `perform(_:)`/ `performAndWait(_:)`; or setting up a basic parent-child context via `parent` -> managed-object-context-crud.md- Building an `NSFetchRequest<T>` with a `predicate`/`sortDescriptors`; calling `context.fetch(_:)`; or declaring `@FetchRequest` in a SwiftUI view -> fetching-with-nsfetchrequest.md- Choosing an `NSDeleteRule` value (`.cascadeDeleteRule`/ `.nullifyDeleteRule`/`.denyDeleteRule`/`.noActionDeleteRule`); reasoning about what happens to related objects on delete; or diagnosing a relationship missing its `inverseRelationship` -> relationships-and-delete-rules.mdNever load more than the contracts relevant to the specific question.## Stop ConditionsStop and report if the requested topic has no matching Knowledge Contractin knowledge/core-data/ — do not guess or fall back to general knowledge.- `NSPersistentCloudKitContainer`/CloudKit sync — Deferred- Lightweight and mapping-model migration (`NSMigrationManager`, versioned/mapping models) — Deferred- `NSFetchedResultsController` — Deferred; do not fabricate its behavior from `fetching-with-nsfetchrequest`- Multi-context concurrency beyond one parent-child relationship — Deferred- SwiftData interop or migration (`@Model`, `ModelContainer`, `ModelContext`) — owned by `swiftdata`; do not answer SwiftData questions from Core Data contracts or fabricate a shared API surface

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