An ObjectiveC source set contains a set of source files, together with an optional set of exported header files.

 apply plugin: "objective-c"

 model {
     components {
         main(NativeLibrarySpec) {
             sources {
                 objc {
                     source {
                         srcDirs "src/main/objectiveC", "src/shared/objectiveC"
                         include "**/*.m"
                     }
                     exportedHeaders {
                         srcDirs "src/main/include"
                     }
                 }
             }
         }
     }
 }