Hey there! I’m trying to integrate our multiplatfo...

# ios

[Marc Reichelt]

Hey there! I’m trying to integrate our multiplatform framework into a big iOS project, where we use project.yml to generate the xcodeproj file. Did anyone manage to do this? I’m following the blog post https://blog.jetbrains.com/kotlin/2021/07/multiplatform-gradle-plugin-improved-for-connecting-kmm-modules/ to use the embedAndSignAppleFrameworkForXcode task, but I can’t even get it working by manually adjusting the Xcode settings - it won’t find the module.
Did anyone achieve this using project.yml? Thank you!

[Marc Reichelt]

PS: I can’t find any documentation at all on kotlinlang.org about the embedAndSignAppleFrameworkForXcode task. Is somebody working on that? This seems like an important gap in the docs right now.

[Marc Reichelt]

PS: If anyone ever wondered where the source for this task was, I found it at https://github.com/JetBrains/kotlin/blob/master/libraries/tools/kotlin-gradle-plug[…]org/jetbrains/kotlin/gradle/plugin/mpp/apple/AppleXcodeTasks.kt

[hfhbd]

Do you use this tool? https://github.com/yonaskolb/XcodeGen
Sounds nice, will try it out. Maybe a candidate for KGP/Amper too

[Marc Reichelt]

Yes, exactly - that’s the one 🙂

[Marc Reichelt]

So I managed to modify the project.yml so the embedAndSignAppleFrameworkForXcode task is run ✅ and the framework gets generated! That’s at least half the thing.

For anyone trying this, I’ve had some luck using this:

preBuildScripts:
      - script: |
          env # prints env variables for debugging
          cd "$SRCROOT/../shared"
          ./gradlew :embedAndSignAppleFrameworkForXcode
        name: "Compile shared.framework"
        showEnvVars: true
        basedOnDependencyAnalysis: false

[Marc Reichelt]

However, when I try to include that framework somewhere else, I get the following linker error:

ld: Undefined symbols:
  _OBJC_CLASS_$_ClassA, referenced from:
       in SomeModule.o
  _OBJC_CLASS_$_ClassB, referenced from:
       in SomeModule.o
  _OBJC_CLASS_$_ClassC, referenced from:
       in SomeModule.o
clang: error: linker command failed with exit code 1 (use -v to see invocation)

(real class names have been removed).
Any idea how to pull in that fresh framework into other targets?

[Marc Reichelt]

(ah, well - the linker error actually came from me creating a new target called shared, which will then create a second shared.framework , which of course does not contain the symbols I need - leading to the linker to fail.
But I still don’t know how to use the compiled KMM shared.framework across all our projects modules.

[Marc Reichelt]

So I did more digging into this, and I managed to compile one module manually on the terminal - though I have absolutely no clue how to tell Xcode what I did.
The problem was a 12k big clang command. I put that into a test.sh so I could execute it again and again in a quick way. There are a lot of -F options in there, which specify the framework search paths. The one for the shared.framework was at the end - once I pulled that before all other -F options, the clang command succeeded and created a binary ✅

[Marc Reichelt]

The culprit seems to be a -F option that defines something with EagerLinkingTBDs - does anybody know more about that? This seems to contain a .tbd file with some JSON data about the shared framework, so that gets picked up by clang instead of picking up the real shared.framework . Any ideas would be welcome!

[Marc Reichelt]

This is how the parameter looks like by the way (redacted):

-F/Users/mreichelt/Library/Developer/Xcode/DerivedData/MyProject-fprqwlsbahdjfhwbvkfnwnxjixzpn/Build/Intermediates.noindex/EagerLinkingTBDs/Debug-iphonesimulator

[Marc Reichelt]

This looks like https://developer.apple.com/documentation/xcode/build-settings-reference#Eager-Linking - but the target we use in our project does not have eager linking enabled. Weird.

[Marc Reichelt]

So I found the actual issue. TL;DR: always clear your DerivedData when you make multiple xcodegen/project.yml / Xcode changes.

Longer explanation what happened on my machine:
1. I tried to create a shared target in project.yml, which xcodegen would then put into the Xcode .pbxproj file.
2. The issue with that is: this would create a (Swift) shared.framework , with the actual KMM shared.framework living inside it (under the Frameworks folder) ⚠️
3. Xcode seems to generate an empty EagerLinkingTBDs directory, with a .tbd file - for the Swift shared.framework !
4. Now every module trying to use shared.framework will fail to link, because it will try to link against the TBD version, and definitely not the KMM module.
So in the end, after I cleaned the DerivedData folder, I could successfully import the KMM shared.framework by directly linking it in my desired module SomeModule . ✅

CC @hfhbd

What I didn’t manage to get done yet is: how can I include the shared.framework in multiple Xcode targets, without calling Gradle for each target? Still investigating.