How to hide objects in objective-c library

I am trying to create a static library written in Objective-C. I would like to hide all implementation details from users of this library. In this example, the OneThing object uses other functions built into the library, including SecretThing, which can be used by many things inside the Library (and cannot be hidden inside OneThing). However, I do not want library users to see that OneThing uses SecretThing, or that SecretThing even exists, even if they are poked into the .a file.

@interface OneThing
+ (void) do;
@end
@interface SecretThing
+ (void) undo;
@end
@implementation OneThing
+ (void) do
{
    [SecretThing undo];
}
@end
@implementation SecretThing
+ (void) undo { }
@end

If we compile this and check the symbol table:

% cc -c onething.m
% nm onething.o | grep Thing
0000000000000000 t +[OneThing do]
00000000000002f8 s +[OneThing do].eh
0000000000000040 t +[SecretThing undo]
0000000000000320 s +[SecretThing undo].eh
0000000000000078 S _OBJC_CLASS_$_OneThing
0000000000000050 S _OBJC_CLASS_$_SecretThing
00000000000000a0 S _OBJC_METACLASS_$_OneThing
00000000000000c8 S _OBJC_METACLASS_$_SecretThing
0000000000000128 s l_OBJC_$_CLASS_METHODS_OneThing
00000000000001d8 s l_OBJC_$_CLASS_METHODS_SecretThing
0000000000000190 s l_OBJC_CLASS_RO_$_OneThing
0000000000000240 s l_OBJC_CLASS_RO_$_SecretThing
0000000000000148 s l_OBJC_METACLASS_RO_$_OneThing
00000000000001f8 s l_OBJC_METACLASS_RO_$_SecretThing
% 

, OneThing SecretThing , . - SecretThing OneThing . , , ( , ):

% ld -r onething.o -exported_symbol "+[OneThing do]" -o onlyonething.o

, "+ [OneThing do]" "T", ( ), "". . , , , , , , ld ( "ld -v" == ld64-133.3), -.

, , , . , , , .

, , , , . , , .

# Move OneThing and SecertThing into their own files, with their own .h
% cat c_api.m
#include "OneThing.h"

void one_thing_do()
{
    [OneThing do];
}
% cc -c c_api.c
% cat main.m
int main(int argc, char**argv)
{
    extern void one_thing_do();

    one_thing_do();
}
% cc main.m c_api.o onething.o secretthing.o -framework Foundation
% ./a.out
% ( runs to completion, no errors )

, :

% ld -r c_api.o onething.o secretthing.o -o strip_c_api.o -exported_symbol "_one_thing_do"
% strip -x c_strip_c_api.o
% nm strip_c_api.o
0000000000000118 s EH_Frame1
0000000000000098 s EH_Frame1
00000000000000d8 s EH_Frame1
                 U __objc_empty_cache
                 U __objc_empty_vtable
                 U _objc_msgSend
0000000000000000 T _one_thing_do
0000000000000130 s func.eh
00000000000000f0 s func.eh
00000000000000b0 s func.eh
0000000000000020 t l001
0000000000000060 t l002
0000000000000170 s l003
0000000000000190 s l004
00000000000001d8 s l005
0000000000000220 s l006
0000000000000240 s l007
0000000000000288 s l008
00000000000002f0 s l009
0000000000000318 s l010
0000000000000340 s l011
0000000000000368 s l012
% clang main.m strip_c_api.o -framework Foundation
% ./a.out
% nm a.out
0000000100001280 S _NXArgc
0000000100001288 S _NXArgv
0000000100001298 S ___progname
0000000100000000 T __mh_execute_header
                 U __objc_empty_cache
                 U __objc_empty_vtable
0000000100001290 S _environ
                 U _exit
0000000100000db0 T _main
                 U _objc_msgSend
0000000100000de0 T _one_thing_do
0000000100001000 s _pvars
                 U dyld_stub_binder
0000000100000d70 T start