linker command failed with exit code 1 (use -v to see invocation)

----------------------------------------

SchemeBuildError: Failed to build the scheme "TestSwiftAA"

linker command failed with exit code 1 (use -v to see invocation)

Link /Users/yann/Library/Developer/Xcode/DerivedData/TestSwiftAA-gbvwptecbqgpoefvtfsbpvwkacta/Build/Intermediates.noindex/Previews/TestSwiftAA/Products/Debug-iphonesimulator/PackageFrameworks/ObjCAA.framework/ObjCAA:
Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_NSObject", referenced from:
      _OBJC_CLASS_$_KPCAADate in ObjCAA.o
  "__objc_empty_cache", referenced from:
      _OBJC_CLASS_$_KPCAADate in ObjCAA.o
      _OBJC_METACLASS_$_KPCAADate in ObjCAA.o
  "_objc_msgSend", referenced from:
      -[KPCAADate initWithYear:month:day:usingGregorianCalendar:] in ObjCAA.o
      -[KPCAADate initWithYear:month:day:hour:minute:second:usingGregorianCalendar:] in ObjCAA.o
      -[KPCAADate initWithJulianDay:usingGregorianCalendar:] in ObjCAA.o
  "_objc_msgSendSuper2", referenced from:
      -[KPCAADate init] in ObjCAA.o
      -[KPCAADate initWithWrappedDate:] in ObjCAA.o
  "_OBJC_METACLASS_$_NSObject", referenced from:
      _OBJC_METACLASS_$_KPCAADate in ObjCAA.o
  "_objc_retain", referenced from:
      -[KPCAADate init] in ObjCAA.o
      -[KPCAADate initWithWrappedDate:] in ObjCAA.o
      -[KPCAADate initWithYear:month:day:usingGregorianCalendar:] in ObjCAA.o
      -[KPCAADate initWithYear:month:day:hour:minute:second:usingGregorianCalendar:] in ObjCAA.o
      -[KPCAADate initWithJulianDay:usingGregorianCalendar:] in ObjCAA.o
  "_objc_storeStrong", referenced from:
      -[KPCAADate init] in ObjCAA.o
      -[KPCAADate initWithWrappedDate:] in ObjCAA.o
      -[KPCAADate initWithYear:month:day:usingGregorianCalendar:] in ObjCAA.o
      -[KPCAADate initWithYear:month:day:hour:minute:second:usingGregorianCalendar:] in ObjCAA.o
      -[KPCAADate initWithJulianDay:usingGregorianCalendar:] in ObjCAA.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)