Your post makes no sense. On the one hand, you claim to "know C++ forward & backward" and on the other, you claim you "don't know Objective-C". You seem to think you cannot teach yourself Objective-C quickly and easily. That does not portent well for your ability to solve problems and learning quickly.

How about taking an afternoon (or however long it takes you) to learn Objective-C. After all,it is just another C variant and closely related to C and C++, which you already know.

Whether you are employable as a developer depends on your programming skills which are separate and distinct from the particular language(s) you "know".