| Radar Number | Status |
|---|---|
| rdar://42326672 | Duplicate of 19245651 |
| openradar://42326672 | Duplicate of 19245651 |
This project demonstrates an Xcode compilation error encountered when building a mixed Swift/Objective-C application test target.
When importing the automatically generated Swift header from an Objective-C test case, Xcode will report that the main app target imported from this header could not be found.
The original issue was raised by this commit on the Wire app: b30e985.
The main application module, Dogs, defines a custom collection view layout and a delegate for this layout (VerticalColumnCollectionViewLayoutDelegate).
Dogs also defines an abstract UICollectionViewController subclass that uses this layout and implements its delegate, VerticalColumnCollectionViewController.
Dogs defines a class in Objective-C, which is imported in Swift through a bridging header, but not used in the abstract class mentioned above.
The test target contains two support classes defined in Swift:
- a random text generator (
Random) that is used in an Objective-C test case (equivalent of mocks/etc... defined in Swift in the Wire test module and imported in Objective-C test cases) - a subclass of
VerticalColumnCollectionViewControllerthat is not used in an Objective-C test case (ColorViewController).
The test target also defines a base test case that all test cases subclass (BaseTestCase). This class is exposed to Swift through the tests' bridging header, which also imports the main application module's bridging header.
The file in which ColorViewController is declared imports Dogs as @testable.
The first test case is written in Objective-C. It tests the Random class. It imports it using the automatically generated Swift interface header ("DogsTests-Swift.h").
The second test case is written in Swift. It tests the VerticalColumnCollectionViewController abstract class behavior, through the concrete ColorViewController subclass defined in the test target. It imports the main application module as @testable.
The main application target builds, runs, and works as expected.
The compilation error occurs when building the test target:
- Hit
CMD-Uto start the tests - The main application module compiles ✅
- The Swift sources in the test target compile ✅
- When compiling the first test case written in Objective-C, compilation stops because the module
Dogs(main app target), imported by the Swift interface header, could not be found.
We think that the problem lies in the ColorViewController definition.
When you define it as a subclass of UICollectionViewController, instead of VerticalColumnCollectionViewController, the test suite will compile and run on the simulator.
We added comments in the ColorViewController.swift file to help you reproduce the issue.
Trying to make VerticalColumnCollectionViewController and related objects public or @objc was not helpful.
The pictures of golden retrievers used in the main app were imported from Unsplash.
This example project does not use any parts of the Wire application. It is licensed under the terms of the MIT license. See the LICENSE file for details.