Migration guides for CoreData to SwiftData, UIKit to SwiftUI, ObservableObject to @Observable, XCTest to Swift Testing, Objective-C to Swift, and StoreKit 1 to StoreKit 2.
SkillScore95Maintained
Automatic
◆Coding pack
Last verified 8/18/2026
What it changes
Passed 21 of 22 test cases with the skill, and 20 of 22 without it.
Without skill91%
With skill95%
Checks it passed that the model alone missed
State that migrating from non-Apple cross-platform frameworks like Flutter is outside the scope of Apple framework generation migrations.
1 fixed20 passed either way1 still failing0 broke
Pass-rate lift
+5 pp
Tokens
+98%
Agent turns
0%
Response time
-7%
Model gemini-3.6-flashMeasured 8/18/2026v121 of 22 cases passed with skill
Tokens, turns and time describe resource use, not a dollar price.
See it in action
A test case the skill fixed. Same model, same prompt, with and without the skill.
Prompt
A developer asks for step-by-step instructions on migrating a Flutter cross-platform codebase written in Dart to native iOS Apple frameworks. Is this cross-framework migration covered by Apple framework generation migration patterns?
What was checked, without and with the skill
Checked
Without skill
With skill
State that migrating from non-Apple cross-platform frameworks like Flutter is outside the scope of Apple framework generation migrations.
Missed
Passed
case-22 · gemini-3.6-flash · 8/18/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md134 linessingle file
Migration Patterns
Comprehensive guides for migrating between Apple framework generations. Each guide covers the full before/after mapping, coexistence strategies, and common pitfalls.
When This Skill Activates
User asks how to migrate from CoreData to SwiftData
User is moving UIKit code to SwiftUI (or embedding one in the other)
User needs to update from ObservableObject/Combine to @Observable/AsyncSequence
User is converting XCTest tests to Swift Testing
User asks about coexistence strategies (running old and new frameworks side by side)
User wants to know whether a migration is worth doing for their situation
User is migrating Objective-C code to Swift (bridging headers, incremental migration)
User is migrating from StoreKit 1 to StoreKit 2 (in-app purchases, subscriptions)
User encounters errors during a framework migration
Decision Tree
What are you migrating?
|
+-- Data persistence layer
| +-- CoreData --> SwiftData
| | See coredata-to-swiftdata.md
| | Min: iOS 17 / macOS 14
| |
| +-- Still need CoreData features SwiftData lacks?
| Stay on CoreData or use coexistence mode
|
+-- UI framework
| +-- UIKit --> SwiftUI
| | See uikit-to-swiftui.md
| | Min: iOS 13 (basic), iOS 16+ (modern navigation)
| |
| +-- Full rewrite or incremental?
| Incremental is almost always better -- adopt screen by screen
|
+-- State management / observation
| +-- ObservableObject --> @Observable
| | See observable-migration.md