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🅾️ Objective-C: iOS interview questions

1. How does message passing work in Objective-C? Middle PRO
2. What is the isa pointer? Senior PRO
3. MRC vs ARC — what's the difference? Middle PRO
4. What is a retain cycle and how do you break it in Obj-C? Middle PRO
5. Property attributes: strong, weak, copy, assign — when to use which? Middle PRO
6. What are categories and class extensions? Middle PRO
7. How do blocks work and why is __block needed? Senior PRO
8. What are KVC and KVO? Middle PRO
9. How does an Obj-C protocol differ from a Swift protocol? Middle PRO
10. Tell us about the Objective-C runtime. Senior PRO
11. What happens when we call a method on a nil pointer? Middle PRO
12. What root classes exist in iOS, and why are they needed? Middle PRO
13. How do you simulate multiple inheritance? Middle PRO
14. Which operations are fast in NSSet vs NSArray? Middle PRO
15. How does #include differ from #import? Middle PRO
16. What are isKindOfClass and isMemberOfClass for? Junior PRO
17. When is it better to use copy for NSString, and why? Middle PRO
18. Why don't we use strong for an enum in Objective-C? Junior PRO
19. What are @synthesize and @dynamic in Objective-C? Middle PRO
20. Objective-C Middle PRO
21. Compiler directives Middle PRO
22. Pointer and reference Middle PRO
23. Forward invocation Senior PRO
24. nil, Nil, NULL, NSNull Middle PRO
25. NSCoding, archiving Middle PRO
26. The id type Middle PRO
27. How does objc_msgSend work, and selector caching? Senior PRO
28. AnyObject vs Any vs NSObject vs id — the difference Middle PRO
29. What is method swizzling and when to use it? Senior PRO