IOS Interview Questions with Answers

If you are in the market of creating an app that is Apple-friendly, and unsure of what to ask in an interview, no worries. We have the iOS questions and answers for any experience level.

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IOS Interview Questions with Answers

Although Apple offers a smaller variety of apps than its competitors, their iPhone now holds a majority of the US market share for the first time. However, globally, Android devices continue to dominate the device market. Despite iPhone's having a global market share of only 15%, iOS apps accounted for 63% of app revenue in 2021.

With Apple fans providing a profitable market for iOS apps, skilled Swift developers are in high demand and command high salaries. While iOS development is generally considered easier than Android development, it still requires a high level of specialized knowledge. The following iOS interview questions and answers will help you determine if an applicant is skilled enough to meet your needs.

 iOS Interview Questions About Data

Data and data structures are crucial in iOS development because they provide a way to store and organize the information used by an app. Appropriate data structures allow developers to efficiently store and retrieve data, which is essential for creating a smooth and responsive user experience. Here are some questions related to data and data structures in iOS development:

What is the difference between a dictionary and an array, and when would you use each?

In iOS, a dictionary is a collection data type that stores key-value pairs. A dictionary is an unordered collection, so the order that items are added to the dictionary doesn't matter and can't be relied upon. Dictionaries are useful for storing data that needs to be quickly retrieved using a unique identifier, known as a key.

An array is an ordered collection of items. Arrays are useful for storing data that needs to be accessed in a specific order or when you need to efficiently perform operations such as inserting, deleting, or accessing items by their index. In iOS, arrays can store items of any type, including other arrays and dictionaries.

A good guideline is to use a dictionary when you need to quickly find a value based on a unique key and use an array when you need to store and access items in a specific order.

Explain tuples

A tuple is a grouping of values containing values of different types. It's similar to an array, but the values in a tuple don't have to be of the same type. Tuples are often used to return multiple values from a function or method or to store a small number of values that are related to each other.

Tuples are a useful way to group related values and are convenient when you need to return multiple values from a function or method. However, they're not as flexible as other data types, such as arrays or dictionaries, and they may not be the best choice for storing large amounts of data.

What are classes and structs in Swift?

Classes and structs are two methods of defining custom data types in the Swift programming language.

A class is a reference type that defines a blueprint for an object. It can contain properties (variables) and methods (functions) that define the object's behavior. A class can also have an initializer — a special method called when an instance of the class is created.

A struct is a value type that defines a collection of related variables and/or functions. Like a class, a struct can have properties and methods. Unlike a class, a struct is passed by value rather than by reference. When you pass an instance of a struct to a function or assign it to a new variable, a copy of the original struct is made.

What is the Codable protocol?

The Codable protocol in Swift is a type that can convert itself into and out of an external representation, such as JSON. It combines the Encodable and Decodable protocols into a single requirement for transferring and saving data.

The Codable protocol is used to serialize and deserialize data, which converts data from one format to another. In Swift, it's often used to convert data from a native Swift object, such as a struct or class, into a format that can be stored or transmitted, such as a JSON, and then convert it back into a native Swift object when needed.

iOS Interview Questions About Design Patterns

These questions cover the design patterns, code architecture, and programming approaches most relevant in iOS development.

What is MVC, and how is it used on iOS platforms?

MVC stands for Model-View-Controller. It's a software architectural pattern that separates the representation of information from the user's interaction with it. The model is the data, the view is the visual representation of the data, and the controller is the code that manages the interaction between the model and the view.

In iOS, MVC is commonly used to structure the development of iOS apps. The model represents the data and business logic of the app, the view is the user interface (UI) elements displayed on the screen, and the controller is the code that mediates between the model and the view.

Using MVC can help to make an iOS app modular and easier to maintain because it separates the different aspects of the app into distinct components. A modular codebase is easier to understand and allows you to change specific parts of the app without affecting other parts.

Explain MVVM in the context of Apple products

Model-View-ViewModel (MVVM) is a software design pattern that separates an application's user interface (UI) into three parts: the model, the view, and the viewmodel.


The model represents the data and the business logic of the application and is responsible for managing the data and making it available to the view.


The view is the UI of the application and is responsible for presenting the data to the user and handling user input.


The view model is a mediator between the model and the view. It exposes the data from the model to the view and handles UI logic. It also translates user actions and input into commands sent to the model.

Uses of MVVM in iOS

MVVM is often used in developing iOS applications because it helps cleanly separate the UI from the underlying logic and data, making it easier to maintain and test the application. It is especially useful when working with large, complex applications where the UI and the data model can change frequently.

To use MVVM in an iOS application, you would typically define your model and viewmodel classes and then use them to bind the data and UI logic to the view in your application. Several frameworks available can help with this process, including ReactiveCocoa and Bond.

What is dependency injection, and why is it useful?

Dependency injection is a software design pattern that allows a programmer to remove hard-coded dependencies and make it possible to change them, whether at run-time or compile-time. In iOS development, dependency injection refers to injecting or passing dependencies like objects or services into an object or class rather than creating them directly within the class.

Dependency injection can be useful for several reasons:

  • It allows for more modular and reusable code.
  • It can make it easier to write unit tests since dependencies can be mocked or stubbed.
  • It can make it easier to maintain the codebase by making it easier to change or update dependencies.

Explain what a singleton is and when you should use it

A singleton is a design pattern that restricts the instantiation of a class to one object. This can be useful when you need to ensure that there is only one instance of a particular class in your app and that instance is shared across the entire application.

There are several reasons why you might want to use a singleton in your iOS apps:

  • To provide a global point of access to a shared resource or service.
  • To ensure that a resource or service is initialized only once and remains in memory for the app's lifetime.
  • To allow multiple objects to access a shared resource or service without passing around a reference to that resource or service.

Singletons can make testing and maintaining your code more difficult. They can also make it harder to reason about the state of your app because there's only one instance of the object that can be accessed from anywhere in the code. Because of their possible drawbacks, singletons should only be used when necessary.

iOS Interview Questions About iOS Frameworks

These questions will allow you to determine how much experience a candidate has with Apple's most commonly used frameworks and APIs.

What are SwiftUI and UIKit, and when should you use one over the other?

SwiftUI and UIKit are both frameworks for building user interfaces on Apple platforms. UIKit has been around since 2008, when it was publicly released. SwiftUI is much newer — it launched in 2019 with iOS 13.


UIKit is a framework that provides a set of classes and functions for developing user interfaces in iOS. It was written in the Objective-C language and provides the basic infrastructure for building and managing iOS apps.

Some of the main features of UIKit include:

  • User interface controls: UIKit provides a wide range of user interface controls, such as buttons, labels, text fields, and table views, that you can use to build your app's user interface.
  • View hierarchy: UIKit uses a view hierarchy to manage the layout and rendering of your app's user interface. You can use this hierarchy to build complex layouts by adding and positioning views within other views.
  • Event handling: UIKit provides support for handling user input events, such as touches and gestures, and for responding to changes in the state of your app's user interface.
  • Animation: UIKit supports animating changes to your app's user interface, allowing you to create smooth and engaging user experiences.
  • Data management: UIKit supports managing and displaying data in your app, including support for table views and collection views.
  • Accessibility: UIKit supports making your app accessible to users with disabilities, including support for dynamic text sizes, VoiceOver, and other accessibility features.


SwiftUI is also a framework for building user interfaces for iOS apps. It's written in the Swift programming language and is gradually replacing UIKit for many iOS applications.

Some of the main features of SwiftUI include:

  • Declarative syntax: SwiftUI uses a declarative syntax, which means you can describe the desired behavior and appearance of your user interface, and SwiftUI will automatically generate the code necessary to make it happen.
  • Automatic support for Dark Mode: SwiftUI makes it easy to support Dark Mode in your apps, allowing users to switch between a light and dark interface.
  • Live Preview: SwiftUI provides a Live Preview feature that lets you see how your user interface will look and behave in real-time as you build it without running the app on a simulator or device.
  • Accessibility: SwiftUI includes built-in support for accessibility features such as VoiceOver, which allows users with visual impairments to use your app.
  • Platform-specific design: SwiftUI includes tools for designing user interfaces specific to each platform, such as the ability to use iOS-style navigation or macOS-style menus.

UIKIt vs. SwiftUI

Several factors will dictate whether you should use the long-established UIKIt or choose the newer SwiftUI for your project. The main two considerations include:

App complexity: SwiftUI is a relatively new framework, and while it has made significant progress in a short amount of time, it doesn't have the depth and breadth of features that UIKit offers. If you're building a complex app that requires a wide range of features and behaviors, or if you need to integrate with legacy code that uses UIKit, you may be better off using UIKit.

Future maintenance: SwiftUI is designed to make it easier to maintain and update your app's user interface over time. If you expect to update your app's user interface frequently or want to minimize the amount of code you have to write and maintain, you may find it more efficient to use SwiftUI.

What is CGAffineTransform, and when would you use it?

CGAffineTransform is a data type used to represent a 2D affine transform in Core Graphics. It can be used to transform graphical elements in the following ways:

  • Scaling a view or other graphical element by a specific factor in the x and y dimensions
  • Rotating a view or other graphical element by a specific angle
  • Translating a view or other graphical element by a specific distance in the x and y dimensions
  • Applying multiple transformations to a view or other graphical element by using the CGAffineTransformConcat function

iOS Interview Questions About Accessibility in Development

Accessibility is tremendously important for developers. Prioritizing accessibility ensures your app is optimized for all users and reduces your risk of litigation. Developers need to think beyond hearing and visual limitations regarding accessibility. Although you certainly want to include users with disabilities, the ultimate goal is to provide a better experience for all users through improved accessibility features.

Explain Dynamic Type

The Dynamic Type feature lets your users adjust the font size to whatever they prefer. They can choose to make the text within an app larger or smaller, making it easier for them to read.  All apps should be designed to support Dynamic Type. You can use the UIFont's class's preferredFont(forTextStyle:) to achieve this. This method will give the appropriate font, including particular text styles, headlines, headings, and paragraphs. The user's preferred font size is set as the default, for intuitive use.

What features can you add to an app to make it more accessible to all users?

In addition to Dynamic Type, apple provides several other features developers can take advantage of to improve accessibility, including:


VoiceOver gives audible descriptions of the different elements on the screen so users can interact with them.

Guided Access

Guided Access locks a user's screen onto one app. This prevents them from clicking away from the app in use accidentally.

Switch Control

Switch Control allows users to control their devices with one or more external switches.


The magnifier feature lets users zoom in on selected areas of the screen, so it's easier to read small type or find clickable buttons.

Closed captions

Closed captions display text on the screen corresponding to the audio being played.

Hire iOS App Developers

While the tech talent shortage persists, the recent mass tech layoffs complicate the hiring picture even more. Finding and hiring iOS developers is a time and resource intensive endeavor. Working with a talent development partner like Revelo can make the hiring process much easier. Our pre-vetted, top-notch engineers are based in Latin America, in time zones that are aligned with the United States for ease of collaboration. They're fluent in English and skilled in the latest tech stacks.

Our clients are usually matched with highly qualified developers within three days, and most hire within three days of being matched. Once you've hired the developers you need, we'll handle the onboarding process. Our dedicated teams take care of administrative HR tasks such as payroll, benefits, taxes, and local compliance so you can focus on scaling your business.

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