Update for CMake 3.16 and later: CMake added native support for Objective-C in version 3.16. The corresponding language strings are OBJCand OBJCXX. Thanks to the square headers for pointing this out .
Original answer: language support is platform dependent.
CMake C, CXX Fortran " " . . Modules/Platform.
, , LANGUAGE project enable_language, , CMake . , CMake, C C++. , , ( , , - ).
Objective-C: C Objective-C, . , C, Objective-C.
, angular . , CMake Objective-C , , , .