15 Interview-questions that you will be asked as an iOS Developer

7 min readDec 21, 2022

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In this article, I am going to share with you 15 possible questions that you will be asked as an iOS Developer during the interview.

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Becoming an iOS Developer is not an easy task, but getting a job can be harder than this in some cases. To get a job, we need to prove our knowledge and abilities. In this article, you are going to make yourself familiar with 15 questions that you will be asked during your interview.

What is Swift?
Answer: Swift is a compiled programming language developed by Apple in June 2014 to develop applications for mobile and desktop. This language works for watchOS, macOS, iOS and tvOS.
Apple created the Swift language to work with both Cocoa Touch and Cocoa. Swift supports multiple operating systems such as Free BSD, Linux, Darwin, etc. This language is designed to work with the Objective-C library and Cocoa framework in Apple products.
What are the advantages of using Swift?
Answer: The Swift programming language has become one of the fastest growing languages in memory. Swift allows us to develop incredibly fast, robust and secure software.
This language is the most useful programming language used to develop an application for macOS and iOS (iPad and iPhone).
Developing apps for macOS and iOS using Swift has some important advantages.
Open source language: The Swift programming language was created as open source and is open to everyone, which makes it easy to regularly upgrade all the source code, mailing lists and bug tracker.
Easy to learn and maintain: The Swift programming language is simpler and more accurate compared to C/C++. Apple developed the programming language to be easy to use and its syntaxes are taken from programming languages such as C#, Python and Ruby. This simple syntax of this programming language makes it more expressive. In Swift, the entire contents of the application (.m) and header (.h) files are combined into a single file, which is (.swift).
Supported by multiple devices: The Swift programming language is not only limited to supporting Apple devices, but will also support multiple devices of the technology world, such as Linux and Windows devices.
Supports dynamic libraries: Dynamic libraries are executable pieces of code that can be linked to an application. This feature allows for the latest fast programming language. Quickly, dynamic libraries are loaded directly into memory, thus resulting in a reduction in the initial size of the application and finally improving application performance.
Optional types: A type that may or may not be held as an optional value in Swift. To declare optional we can use a question ‘?’ sign.
Closures: Closures are independent function blocks that can be passed and used in our code.
Explain difference between Swift and Objective-C.
Answer: I listed in below the various differences between Swift and Objective-C.
* Swift is an object-oriented and functional programming language, while Objective-C is a class-based object-oriented programming language.
* Swift supports dynamic libraries, while Objective-C does not support dynamic libraries.
* Swift supports Tuples, while Objective-C does not support Tuples.
* Semicolons are not required in Swift, but they are required in Objective-C.
* Swift is an open source programming language, but Objective-C is restricted to Apple and is not an open source language.
* We must use the ‘let’ keyword to declare for a constant and the ‘var’ keyword to declare a variable, whereas in the C target we must declare the variable as ‘NSString’ and the constant as ‘int’.
* Swift allows us to define methods in structure, classes or enumeration, while Objective C does not.
* In Swift we can define classes in a single file (.swift), whereas in Objective C we can create separate interface (.h) files for classes and implementation (.m) files for classes.
What are the tools required to develop iOS applications?
Answer: These are some of the basic tools we must have:
* Mac/MacMini: We need to get a Mac. Don’t worry, if we have our own computer, we can still develop iOS apps through Mac Mini.
* Xcode: Xcode is the Apple IDE (Integrated Development Environment) used for both iOS apps and MAC OS. It provides us with a visual layout editor and a code editor that can handle the logic, user interface and response behind the scenes.
* Swift Programming Language: In the code editor, the logic will be written in a programming language invented by Apple called Swift.
* Apple Developer Program: This program allows the developer to publish our app in the App store so that customers and downloaders from all over the world can download and use our app.
What are the most important features of Swift?
Answer: Some important features of Swift are given below:
* More expressive structures and enumerations
* Protocol orientated
* Optional Types
* Type Security and Type inference language
* It is not necessary to use semicolons
* Mandatory initiators
* Secure by default
* Less code, fewer files
* Forced Opening
* Tuples
* Closures
* It is much faster than other languages.
Describe common execution states for a quick iOS App (iOS App Lifecycle).
Answer: 5 common execution situations are as follows:
No execution: This is a simple state where our application is not started or no code is executed and terminated by the system and the application is completely closed.
Inactive: This state is only a transitional state. The inactive state means that our application is running in the background but cannot receive events.
Active: The active state is the main execution state in which our application runs in the background and can receive events.
Background: This is the state where our App is running in the background and can still run code in the background.
Suspended: This state means that our running application is in the background and the system has suspended this application and the application cannot execute any code.
Is Swift an object-oriented programming language?
Answer: Yes, swift is an object-oriented programming language.
What kind of objects are the basic data types in Swift?
Answer: Swift uses a standard set of basic data types for different purposes, such as Boolean values, numbers, and strings.
* Int: int is used to store an integer value.
* Double and Float: Double and Float in swift counts when working with decimal numbers.
* Bool: Bool type is used to store Boolean value. It swiftly uses true and false conditions.
* String: In String literal values, the user defines text enclosed in double quotes in Swift.
* Arrays: Arrays are collections of list items.
* Dictionaries: A dictionary is an unsorted collection of items of a particular type linked by a unique key.
What is init () in Swift?
Answer: Initialisation is the process of preparing an instance of an enumeration, structure or class for use.
Initialisers are also called to create a new instance of a given type. An initialiser is an instance method with no parameters. Using the initialiser we can write the keyword init.
What is the difference between Swift and Let and Var?
Answer: Check my article -> Reference and Value types in Swift — What are they?
What is Plist in iOS?
Answer: Plist stands for Property List. Plist is basically a dictionary of values and keys that can be stored in our file system with .plist file extension. Property list is used as a portable and lightweight tool to store smaller amount of data. They are normally written in XML.
What is Protocol in Swift?
Answer: Protocol is a very common feature of the Swift programming language, and protocol is a concept similar to an interface from java. A protocol defines a blueprint of properties, methods, and other requirements appropriate to a particular task.
In its simplest form, a protocol is an interface that describes some methods and properties. A protocol is defined as a skeleton of properties or methods rather than an implementation. The implementation of properties and methods can be done by defining enumerations, functions and classes.
Protocols are declared after structure, enumeration or class type names. Single and multiple protocol declarations are possible. Multiple protocols are separated by commas.
We can define a protocol in a very similar way to structures, enumerations and classes:
Protocol Someprotocol { // protocol definition goes here }
We can define multiple protocols separated by commas:
Class SomeClass: SomeSuperclass, Firstprotocol, Secondprotocol { // Structure definition goes here }
What is a delegate in Swift?
Answer: A delegate is a design pattern used to pass data or communication between structures or classes. A delegate allows messages to be sent from one object to another object when a specific event occurs and is used to handle table view and collection view events.
How to create a constant in Swift?
Answer: To declare a constant in Swift, we must use the ‘let’ keyword.
What are the user interface elements?
Answer: Images, buttons, labels, text fields and all other elements that can be seen by the user in the application are called UI elements.

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15 Interview-questions that you will be asked as an iOS Developer

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