| name | migration-patterns |
| description | Generic reference for Objective-C to Swift and XCTest to Swift Testing migrations. Background material only — for this repo's ObjC to Swift work, docs/migration/playbook.md is authoritative. |
| allowed-tools | ["Read","Glob","Grep"] |
Migration Patterns
Generic, non-repo-specific migration references retained as background reading.
Authority note. This repo's ObjC → Swift migration is governed by
docs/migration/playbook.md, plus agents/xcodebuild/SKILL.md (build-error triage) and
agents/review/SKILL.md (review checklist). Those are derived from actual build failures in
this codebase. Where the generic objc-to-swift.md below disagrees with them, the playbook
wins. See "Known conflicts" for the specific points.
Available guides
| Migration | Reference File | Status in this repo |
|---|
| Objective-C to Swift | objc-to-swift.md | Active — but see playbook first, and the conflicts below |
| XCTest to Swift Testing | xctest-to-swift-testing.md | Not adopted — 194 files use XCTestCase, 0 use Swift Testing |
Known conflicts between objc-to-swift.md and this repo
Four points where following the generic guide would break this SDK:
-
@objc naming. The guide only ever shows bare @objc class Foo: NSObject. The
parenthesized form @objc(PBMFoo) never appears in it. This repo has 153 @objc(PBM…)
declarations, and they exist to preserve the shipped ObjC API name while the Swift type drops
the prefix. Omitting it silently renames a public class. See playbook "Naming convention".
-
Value types. The guide advises converting NSObject subclasses to structs
(objc-to-swift.md:25, :121). Phase 1–3 ORTB twins must stay @objc NSObject
subclasses because ObjC parameter builders still consume them — playbook Gap 4.
-
Bridging headers. The guide makes them central. The PrebidMobile framework target has
no bridging header and cannot use one; only the test target does. See playbook Gap 8 on
private-header invisibility in framework builds.
-
The Swift→ObjC import. The guide says #import "ProjectName-Swift.h". This repo must use
#import "SwiftImport.h", a conditional shim — a direct import compiles under CocoaPods and
fails under SPM.
Also absent from the guide entirely: NSCopying (playbook records that .copy() crashes at
runtime on twins that omit it) and the @_spi(PBMInternal) propagation rules.
Why this repo stays on XCTest
Recorded so the question does not get reopened. xctest-to-swift-testing.md:433-441 disqualifies
this repo on two of its own criteria: shared test infrastructure via XCTestCase subclassing, and
ObjC test helpers that depend on XCTestCase. Beyond that, the .xctestplan registry, the ObjC
test bridging header, and the flaky-test isolation procedure in agents/xcodebuild/SKILL.md all
assume XCTest's Class/method addressing.
Note in particular that the generic advice to "migrate tests first for a safety net" is wrong
here — the XCTest suite is the safety net for the ObjC → Swift work, and it gates every
migration PR (./scripts/testPrebidMobile.sh --latest --quick). Dismantling it first would remove
the gate before the risky work begins.
References
