iOS and Swift

Hi All! Here I am after a long time with some important topic.  iOS Interview Questions  Hope these questions will help you..... STUDY WELL. All the best! What are functions? How it differ from Closures? What is the difference between escaping and non escaping closures? How would you avoid retain cycles when using closures in swift? What is capture list? What is difference between unowned and weak? What is protocol? Can we extend protocol? Can we add properties to extensions? What are lazy properties? Are they thread safe? Whats Optional?(Unwrapping techniques) What is difference between if let and guard let? What is difference between Class and Struct? What is Actor? What are initialisers? What is convenience initialiser? What are higher order functions? Tell me life cycle of App Delegate? Life cycle of UIViewController? What are SOLID principles? What you use for persistent storage? Difference between NSSet and NSArray/ Set and Array? What is atomic and nonatmic? What is KVC and KVO?