Philipp <p.stephani2@gmail.com> schrieb am So., 8. Okt. 2017 um 16:16 Uhr:

Visit a file with a file name extension of .h and the following
contents:

@interface foo {
}
- (void)method;
@end

The buffer will be in c-mode, not objc-mode.  CC-Mode should
automatically detect that this is an Objective-C header and switch to
objc-mode.  Probably searching for @interface or @implementation should
cover most cases.

It seems like CC-Mode is already doing something similar with `c-or-c++-mode'. Probably that functionality should be extended to cover Objective-C (and Objective-C++?) as well.