Explanation

This app demonstrates an issue when trying to use the OLMKit pod with the use_frameworks! setting.

The use_frameworks! setting is required in order for a Swift app to use the pods (it is not required for Obj-C development, however).

Try this:

1. pod install - to install all dependencies (Note: 'OLMKit' is not included in the pod file)
2. Run the project (simulator is fine). The app pulls all the public rooms from https://matrix.org. (but encryption won't be supported... gross)
3. Comment out the use_frameworks! setting in the podfile. pod install again.
4. Attempt to build the project. It fails! (Swift errors out at the import MatrixSDK line, complaining that it can't find that module)
5. un-comment use_frameworks! (necessary for Swift), then un-comment pod 'OLMKit' (necessary for encryption) in the podfile. pod install once more.
6. Attempt to build and run the project. It fails! (see below)

Error message

The compiler fails with a Apple Mach-O Linker Error. Here is the text:

Ld /Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Products/Debug-iphonesimulator/OLMKit/OLMKit.framework/OLMKit normal x86_64
cd /Users/averypierce/Projects/Junk/Dummy-Matrix-Client-Swift/Pods
export IPHONEOS_DEPLOYMENT_TARGET=8.0
export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -arch x86_64 -dynamiclib -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator10.2.sdk -L/Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Products/Debug-iphonesimulator/OLMKit -F/Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Products/Debug-iphonesimulator/OLMKit -filelist /Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Intermediates/Pods.build/Debug-iphonesimulator/OLMKit.build/Objects-normal/x86_64/OLMKit.LinkFileList -install_name @rpath/OLMKit.framework/OLMKit -Xlinker -rpath -Xlinker @executable_path/Frameworks -Xlinker -rpath -Xlinker @loader_path/Frameworks -mios-simulator-version-min=8.0 -dead_strip -Xlinker -object_path_lto -Xlinker /Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Intermediates/Pods.build/Debug-iphonesimulator/OLMKit.build/Objects-normal/x86_64/OLMKit_lto.o -Xlinker -export_dynamic -Xlinker -no_deduplicate -Xlinker -objc_abi_version -Xlinker 2 -stdlib=libc++ -fobjc-arc -fobjc-link-runtime -lc++ -framework Foundation -single_module -compatibility_version 1 -current_version 1 -Xlinker -dependency_info -Xlinker /Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Intermediates/Pods.build/Debug-iphonesimulator/OLMKit.build/Objects-normal/x86_64/OLMKit_dependency_info.dat -o /Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Products/Debug-iphonesimulator/OLMKit/OLMKit.framework/OLMKit

duplicate symbol _OLMKitVersionString in:
    /Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Intermediates/Pods.build/Debug-iphonesimulator/OLMKit.build/Objects-normal/x86_64/OLMKit.o
    /Users/averypierce/Library/Developer/Xcode/DerivedData/Dummy-Matrix-Client-Swift-hdglxcdleqidcaeerdmokndwkznq/Build/Intermediates/Pods.build/Debug-iphonesimulator/OLMKit.build/Objects-normal/x86_64/OLMKit_vers.o
ld: 1 duplicate symbol for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)