Discover 50 essential interview questions that cover various key areas in iOS development. Clear and concise answers to each question, providing you with the knowledge and understanding you need to impress your interviewers. Code snippets and examples to illustrate key concepts and demonstrate practical application of iOS development principles. In Swift, both structs and classes are used to de?ne properties and methods to add functionality. However, there are key differences in how they are used, which stem from Swift's value type (struct) versus reference type (class) distinction. Understanding these differences is crucial for making informed decisions about when to use each in your iOS applications. Object-Oriented Programming (OOP) is a programming paradigm that organizes code into objects, which are instances of classes. OOP focuses on creating classes that encapsulate data and behavior, and objects interact with each other through methods and properties. The main concepts of OOP are encapsulation, inheritance, and polymorphism. On the other hand, Protocol-Oriented Programming (POP) is a programming paradigm that puts protocols at the center of the design. In Swift, protocols de?ne a blueprint of methods, properties, and requirements that conforming types must implement. POP focuses on de?ning behavior through protocols and then implementing that behavior in concrete types.