Suggested approach: Although Objective-C is has largely lost its grip on the enterprise it’s still going to be a useful skill for some years yet, and if the company you're interviewing with has extensive Objective-C code then hopefully you can produce a strong answer here.
Make sure and talk about how Swift and Objective-C interact using bridging headers – it's unlikely you'll join a job where you write new Objective-C, but you do at least need to know how to make Objective-C and Swift play well together.
Estimated difficulty: Intermediate
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