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Interview questions: Introduction

Getting ready for a job interview is tough work, so I’ve prepared a whole bunch of common questions and answers to help give you a jump start. But before you get into them, let me explain the plan in more detail…

Watch the video here, or read the article below

Once you’ve polished your resume, prepped your portfolio, and applied for the job of your dreams, you still have one major hurdle to get through: the interviews, which might be an hour if you’re lucky, or potentially a day or two if it’s for a bigger company or a more senior role.

I’ve done a lot of job interviews in my time, and I’m also responsible for maintaining the world’s largest collection of interview questions for Swift developers – questions that are specifically and directly used by countless companies around the world. So, I tell you the kinds of things you’re likely to be asked in your interview, but that’s not enough by itself.

Yes, if I were to tell you all the most popular interviews questions, it would give you something to plan for and prepare for, and hopefully would give you extra confidence when walking into the interview that you have good answers ready. But it wouldn’t do much to help you structure those answers – it wouldn’t give you guidance on what to include in your answer, or how to structure things, and so on.

So, this section of Hacking with Swift+ is designed to solve that problem: not only have I selected the most common interview questions for you, but I’ve also answered them in detail, explained the approach I would take, and often provided code samples to, so you have the complete toolkit needed to really ace your next interview.

You’ll see a few things come up regularly, and I want to repeat them here:

  1. There’s a lot of value in being pragmatic – in not sticking to one fixed idea because it’s your favorite thing, but instead being able to discuss the advantages and disadvantages of multiple concepts.
  2. It’s often a good idea to list a few possible answers to a question, then pick one or perhaps two to zoom in on and discuss in detail.
  3. Giving a simple, factual answer matters, and is usually the first thing you should do, but make sure you follow it up with some hands-on examples you have from real-world projects, and ideally also some discussion of any nuances or complexities that show you have experience.
  4. Although I’m not a big fan of asking folks to write code while someone is watching them, it’s a good idea to have some simplified examples you can present if needed.
  5. All the best questions lead to open discussion where the interviewee can focus on what interests them or go off on tangents, so look for areas where you can explore topics together and show off your knowledge.

There’s one bonus tip that isn’t about iOS: if they ask you whether you’d like some coffee or something, say yes. I don’t care if you don’t want coffee – ask for tea, or water, or soda, or something, just take the drink. Why? Because when they ask you a tough question, you can take a sip of your drink and pause for just a moment, and in doing so buy yourself a few seconds to phrase your answer as best as you can. Seriously, it works – take the drink!

If you liked this, you'd love Hacking with Swift+…

Here's just a sample of the other tutorials, with each one coming as an article to read and as a 4K Ultra HD video.

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Making the most of optionals



FREE: Making the most of optionals

Swift’s optionals are implemented as simple enums, with just a little compiler magic sprinkled around as syntactic sugar. However, they do much more than people realize, and in this article I’m going to demonstrate some of their power features that can really help you write better code – and blow your mind along the way.

Understanding generics – part 1



FREE: Understanding generics – part 1

Generics are one of the most powerful features of Swift, allowing us to write code once and reuse it in many ways. In this article we’ll explore how they work, why adding constraints actually helps us write more code, and how generics help solve one of the biggest problems in Swift.

Ultimate Portfolio App: Introduction



FREE: Ultimate Portfolio App: Introduction

UPDATED: While I’m sure you’re keen to get started programming immediately, please give me a few minutes to outline the goals of this course and explain why it’s different from other courses I’ve written.

Transforming data with map()



FREE: Transforming data with map()

In this article we’re going to look at the map() function, which transforms one thing into another thing. Along the way we’ll also be exploring some core concepts of functional programming, so if you read no other articles in this course at least read this one!

Introduction – please watch!



FREE: Introduction – please watch!

The Inside Swift series is designed to explore Swift's own source code, so you can better understand how it works and also pick up techniques you can apply to your own code.

Shadows and glows



FREE: Shadows and glows

SwiftUI gives us a modifier to make simple shadows, but if you want something more advanced such as inner shadows or glows, you need to do extra work. In this article I’ll show you how to get both those effects and more in a customizable, flexible way.

Creating a custom property wrapper using DynamicProperty



FREE: Creating a custom property wrapper using DynamicProperty

It’s not hard to make a basic property wrapper, but if you want one that automatically updates the body property like @State you need to do some extra work. In this article I’ll show you exactly how it’s done, as we build a property wrapper capable of reading and writing documents from our app’s container.

Functional programming in Swift: Introduction



FREE: Functional programming in Swift: Introduction

Before you dive in to the first article in this course, I want to give you a brief overview of our goals, how the content is structured, as well as a rough idea of what you can expect to find.

Using memoization to speed up slow functions



FREE: Using memoization to speed up slow functions

In this article you’ll learn how memoization can dramatically boost the performance of slow functions, and how easy Swift makes it thanks to its generics and closures.

Creating a WaveView to draw smooth waveforms



FREE: Creating a WaveView to draw smooth waveforms

In this article I’m going to walk you through building a WaveView with SwiftUI, allowing us to create beautiful waveform-like effects to bring your user interface to life.

How to use phantom types in Swift



FREE: How to use phantom types in Swift

Phantom types are a powerful way to give the Swift compiler extra information about our code so that it can stop us from making mistakes. In this article I’m going to explain how they work and why you’d want them, as well as providing lots of hands-on examples you can try.




FREE: Trees

Trees are an extraordinarily simple, extraordinarily useful data type, and in this article we’ll make a complete tree data type using Swift in just a few minutes. But rather than just stop there, we’re going to do something quite beautiful that I hope will blow your mind while teaching you something useful.

User-friendly network access



FREE: User-friendly network access

Anyone can write Swift code to fetch network data, but much harder is knowing how to write code to do it respectfully. In this article we’ll look at building a considerate network stack, taking into account the user’s connection, preferences, and more.

Understanding assertions



FREE: Understanding assertions

Assertions allow us to have Swift silently check the state of our program at runtime, but if you want to get them right you need to understand some intricacies. In this article I’ll walk you through the five ways we can make assertions in Swift, and provide clear advice on which to use and when.

Flocking with boids



Flocking with boids

If you watch a flock of birds you’ll see it exhibits all sorts of complex behaviors as they swarm around in the air – they often stay together but not too close, they move in the same direction but also seem to change direction at the same time. In this article we will create flocking behavior in SwiftUI, using Craig Reynolds’ classic boids algorithm.

How does CloudKit differ from Core Data?



How does CloudKit differ from Core Data?

Although Apple has done a great deal of work to bring these two powerhouse frameworks closer together, they still fundamentally work in entirely different ways, and providing a good comparison might take more thought than you expect.

What is the difference between the Float, Double, and CGFloat data types?



What is the difference between the Float, Double, and CGFloat data types?

This question is partly technical, partly about keeping up with Swift, and partly about application, and and I suggest you tackle it in that order.

Drink up!



Drink up!

In this article we’re going to build an app to track how much water the user has consumed today, then tie it into a widget so they place a gentle reminder right on their Home Screen.

What’s new in SwiftUI for iOS 17?



What’s new in SwiftUI for iOS 17?

Before we dive into all the new SwiftUI features, there are two remaining Swift language changes I want to talk about. Both are significant, but honestly not worth worrying about – there are far more interesting things to be spending time on!





The SF Symbols app is a great resource for discovering icons, but at the time of writing it’s also only available on macOS. In this article we’ll build our own SF Symbols app for iOS, integrating customization features along the way.

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