For fun I decided to interview ChatGPT as an iOS developer. I asked it the questions I would ask any iOS developer. ChatGPT draws upon readily available answers that are a year old, so the answers can seem a bit dated. Some of the answers are not accurate and some elements have been renamed. eg. NSOperations is now Operations
Explain the difference between Structs and Classes in Swift programing language?
Structs and Classes are both very similar in Swift. They both allow you to create custom data types, used to store related data and functions.
The main difference between Structs and Classes is that Structs are value types, while Classes are reference types. This means that when you assign a Struct to a variable or pass it to a function, the Struct is copied. With Classes, only a reference to the existing instance is used.
Structs are more memory efficient and are used when you want to create simple data structures. Classes are more powerful and are used to create complex objects with relationships. Classes also support inheritance, allowing for re-use of code.
How does memory management work in iOS, and explain reference counting?
iOS memory management is an automatic process that is managed by the operating system. The iOS memory manager is responsible for allocating memory to applications, tracking memory usage and reclaiming memory when it is no longer needed. It works by allocating memory as needed and freeing up memory when it is no longer being used. iOS also helps manage memory by suspending applications when they are not in use. This helps save memory and battery life.
Reference counting is a memory management technique used by iOS to track the number of references to objects in memory. When an object is created, its reference count is set to one. When a reference to that object is passed to another object, the reference count is increased. When the object is no longer needed, the reference count is decreased. When the reference count reaches zero, the object is automatically freed from memory. Reference counting is an effective way to manage memory and ensure that objects are not kept in memory after they are no longer needed.
in swift programing what is an Optional and what type of object is it?
An Optional in Swift is a type that can represent either a value of the specified type or ‘nil’ if the value is missing. Optionals are used to represent values that may or may not exist, and provide a safe way to work with values that may be missing. Optionals are a kind of generic type and can hold any type of value.
Aren’t optionals enums?
No, Optionals are not enums. Optionals are a type that can represent either a value of the specified type or ‘nil’ while enums are a data type that can represent a limited set of values.
[Author’s note: I don’t think this answer is accurate. Options ARE and enumeration type.
@frozen enum Optional<Wrapped>
An enumeration type that represents either a wrapped value or nil, the absence of a value.]
Given the String “kayak” write a Swift function to prove it in a palindrome?
func isPalindrome(string: String) -> Bool {
let reversedString = String(string.reversed())
return string == reversedString
}
let palindrome = isPalindrome(string: "kayak")
print(palindrome) // prints true
Write the same to prove that “Madam, I’m Adam” is a palidrome?
func isPalindrome(string: String) -> Bool {
let removedSpecialCharacters = string.replacingOccurrences(of: "[^a-zA-Z0-9]", with: "", options: .regularExpression)
let reversedString = String(removedSpecialCharacters.reversed())
return removedSpecialCharacters.lowercased() == reversedString.lowercased()
}
let palindrome = isPalindrome(string: "Madam, I'm Adam")
print(palindrome) // prints true
How can you make Core Data multithreaded?
It is possible to make Core Data multithreaded by using managed object contexts. Each thread should have its own managed object context and should not share any resources. To ensure thread safety, managed object contexts should be locked when writing to the persistent store. It is also important to be aware of the potential for deadlocks and use appropriate locking patterns. Additionally, all access to data should be performed on the main thread and any background threads should be used only for reading data.
how can you make Core Data thread safe?
Core Data can be made thread safe by using managed object contexts. Each thread should have its own managed object context and should not share any resources. To ensure thread safety, managed object contexts should be locked when writing to the persistent store. Additionally, all access to data should be performed on the main thread and any background threads should be used only for reading data. It is also important to be aware of the potential for deadlocks and use appropriate locking patterns.
Explain all the ways to set contraints in Xcode?
1. Storyboard: You can set constraints in Xcode’s storyboard by using the Interface Builder. This is a visual way of setting constraints, allowing you to drag and drop elements and position them on the screen.
2. Auto Layout: Auto Layout is a powerful tool built into Xcode that allows you to set constraints for elements in your user interface. With Auto Layout, you can set constraints that control how an element behaves based on the device size and orientation.
3. Size Classes: Size Classes are a feature of Xcode that allow you to set different constraints for different devices. For example, you can set different constraints for iPhones and iPads so that the user interface looks great on both devices.
4. Visual Formatting: Visual Formatting is a powerful language that allows you to set constraints using code. This is useful for when you need more control over the layout than what Auto Layout provides.
5. Layout Anchors: Layout Anchors are a new feature of Xcode that allow you to set constraints based on the position of other elements. For example, you can set a constraint that an element should be positioned a certain number of points from the top of the screen.
What are the pros and cons of native iOS development versus hybrid iOS development?
Pros of Native iOS Development:
– Native apps are built for specific platforms and are written in languages that the respective platform supports. This allows developers to leverage all of the device’s native features and create a more seamless and intuitive user experience.
– Native apps tend to be faster and more reliable than hybrid apps since they are specifically built for the device.
– Native apps can provide better support for device-specific features such as GPS, camera, and more.
Cons of Native iOS Development:
– Native development can be more expensive and time consuming than hybrid development.
– Native apps require more maintenance and updates since they are built for a specific platform.
Pros of Hybrid iOS Development:
– Hybrid apps are cheaper and faster to develop than native apps since they can be built using web technologies such as HTML, CSS, and JavaScript.
– Hybrid apps can be built once and deployed to multiple platforms, making them more cost effective in the long run.
– Hybrid apps can also access device-specific features such as GPS, camera, etc.
Cons of Hybrid iOS Development:
– Hybrid apps may lack the performance and reliability of native apps since they are built using web technologies.
How do you set up an iOS app to use push notifications in Xcode and AppStoreConnect?
1. Create your app identifier in App Store Connect.
2. Enable Push Notifications for your app identifier in App Store Connect.
3. Create a Provisioning Profile for your app identifier with Push Notifications enabled.
4. Download and install the Provisioning Profile in Xcode.
5. In Xcode, enable Push Notifications for your app’s Target.
6. Add the necessary code to your app to register for and receive push notifications.
7. Create a Push Notification Certificate in App Store Connect and download it.
8. Use the certificate in Xcode to configure your app’s push notifications.
9. Test Push Notifications in the iOS Simulator.
10. Submit your app to the App Store.
in an iOS app, how would you fetch an image from a web URL using NSOperations?
You can use NSOperation to fetch an image from a web URL by creating an NSOperation subclass that performs the image download. Inside this subclass you would use an NSURLSession to create a data task and download the image data from the URL. Once the download is complete, you would convert the data into a UIImage object and store it in a property of your NSOperation subclass. Finally, you would call the completion block with the UIImage object as a parameter.
Can you write a code sample?
// Create a subclass of NSOperation that performs the image download
class MyImageFetchOperation: NSOperation {
// Store the image data
var image: UIImage?
// URL from which to download the image
let url: URL
// Completion handler called when the download is complete
let completion: ((UIImage?) -> Void)
// Initializer
init(url: URL, completion: @escaping ((UIImage?) -> Void)) {
self.url = url
self.completion = completion
super.init()
}
// NSOperation main method
override func main() {
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
if let data = data {
self.image = UIImage(data: data)
self.completion(self.image)
}
}
task.resume()
}
}
What if there is an error fetching the image?
If an error occurs while fetching the image, the completion handler will be called with a nil parameter instead of a UIImage object. The caller of the completion handler will then be responsible for handling the error appropriately.
Can you add the error handling to the code?
// Create a subclass of NSOperation that performs the image download
class MyImageFetchOperation: NSOperation {
// Store the image data
var image: UIImage?
// URL from which to download the image
let url: URL
// Completion handler called when the download is complete
let completion: ((UIImage?, Error?) -> Void)
// Initializer
init(url: URL, completion: @escaping ((UIImage?, Error?) -> Void)) {
self.url = url
self.completion = completion
super.init()
}
// NSOperation main method
override func main() {
let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
if let data = data {
self.image = UIImage(data: data)
self.completion(self.image, nil)
} else {
self.completion(nil, error)
}
}
task.resume()
}
}
How would you create a flow for pull requests to a github repo on a large team?
1. Create a policy for pull requests. Define who is responsible for reviewing pull requests, when reviews should be completed, and how long pull requests can remain open.
2. Create a standard template for pull requests. Include information on the project, the changes requested, and the expected outcome.
3. Require all pull requests to be reviewed by at least one other member of the team.
4. Establish a process for resolving conflicts. This could include discussion, voting, or a consensus among team members.
5. Establish a process for merging pull requests. This could include a single person responsible for merging, or a process of consensus-based merging.
6. Establish a process for closing pull requests. This could include closing pull requests that have been open for too long, or closing pull requests after they have been merged.
7. Establish a process for tracking pull requests. This could include a dashboard or checklist to track the status and progress of each pull request.
8. Establish a process for responding to feedback and making changes. This could include incorporating feedback into the pull request, or creating a new pull request with the changes.
How would you prepare for a job interview as an iOS engineer?
1. Research the company and the position: Learn as much as you can about the company, its culture and mission, and the specific job you’re applying for.
2. Practice your answers: Prepare for common questions about your experience, qualifications, and goals.
3. Prepare questions for the interviewer: Asking thoughtful questions shows that you’re engaged and interested in the position.
4. Review coding fundamentals: Refresh your memory of the fundamentals of iOS development, such as Objective-C, Swift, and the iOS SDK.
5. Review your portfolio: Make sure your portfolio is up to date and reflect your best work.
6. Dress professionally: Dress in a professional manner that is appropriate for the industry.
7. Arrive early: Arrive at least 10 minutes ahead of time to ensure that you have plenty of time to relax and get settled before the interview starts.
What if they ask you about SwiftUI?
If a potential employer asks me about SwiftUI, I would explain that SwiftUI is an innovative new user interface framework for iOS apps. I would describe how SwiftUI uses a declarative syntax to make it easier to create complex user interfaces and how it integrates with existing UIKit code to help create a more unified development experience. I would also explain that I have experience with SwiftUI, having built several apps using the framework.
What about React Native or Flutter?
If a potential employer asked me about React Native or Flutter, I would explain that both are popular frameworks for developing cross-platform mobile applications. I would explain that I have experience with React Native, having built several apps using the framework, and that I have also studied Flutter, though I have not yet had the opportunity to build an app using it. I would also discuss the differences between the two frameworks, such as React Native’s focus on JavaScript and Flutter’s use of the Dart language.
If you were to interview a candidate as an iOS engineer, what would ask them about, and would test then on code examples?
1. What experience do you have developing iOS apps?
2. How are you familiar with Swift and Objective-C programming languages?
3. What techniques do you use to debug iOS apps?
4. Can you explain how memory management works in iOS?
5. What techniques do you use to optimize performance of iOS apps?
6. What experience do you have with Core Data and other frameworks such as UIKit, Foundation, and Core Animation?
7. Have you ever used version control systems such as Git?
8. What techniques do you use to test iOS apps?
9. How comfortable are you with submitting apps to the App Store?
Test them on code examples:
1. Create a simple iOS app that displays a list of items.
2. Create an iOS app that allows users to view and edit data stored in a Core Data database.
3. Implement a custom UIViewController subclass that performs some animation when transitioning between screens.
4. Create a simple iOS app that uses GPS to display a user’s current location on a map.
5. Create an iOS app that uses a REST API to fetch and display data.
6. Create an iOS app that uses the camera to
If I give you eight visually identical balls and tell you that only one is heavier than the rest, how would you find the heavy ball?
1. Place two balls on a set of scales and compare the weight of each.
2. If they are the same weight, place one of the two on one side of the scales, and three of the remaining balls on the other side.
3. Compare the two sides of the scales.
4. If the two sides are equal, then the remaining three balls contain the heavy ball.
5. Take two of the three balls and place them on the scales.
6. If they are the same weight, then the remaining ball is the heavy ball.
7. If they are not the same weight, the heavier one is the heavy ball.
Can you find a way to weigh them in the least amount of steps?
Yes, it is possible to find the heavy ball in the least amount of steps.
1. Place three balls on one side of the scales, and three balls on the other side.
2. Compare the two sides of the scales.
3. If the two sides are equal, then the remaining two balls contain the heavy ball.
4. Take one of the two balls and place it on one side of the scales, and the remaining ball on the other side.
5. Compare the two sides of the scales.
6. The heavier one is the heavy ball.
How would you test you iOS app for Accessibilty and what would you add to the app?
1. Use an accessibility testing tool such as VoiceOver to test that all elements of the app are accessible.
2. Check that all images and text fields have appropriate labels and descriptions.
3. Test that all buttons, links and other controls are labeled accurately and can be easily identified by users.
4. Make sure that all interactive elements can be used with only one hand.
5. Check that all text is legible and usable by people with impaired vision.
6. Ensure that all color contrast requirements are met.
7. Test that the app works with a variety of assistive technologies.
To add to the app:
1. Add a “Settings” panel that allows users to adjust the font size, color and contrast to fit their individual needs.
2. Include a tutorial to explain how to use the app with assistive technology.
3. Add custom keyboard shortcuts to allow users to quickly navigate through the app.
4. Include a “skip navigation” button to help keyboard users quickly skip to the main content.
5. Provide audio cues for all interactive elements.
6. Allow users to adjust the voice speed and pitch of the VoiceOver audio.
7. Add a “captions” option to provide subtitles for any audio or video content.
What about color vision issues?
To address color vision issues, you can add an option to adjust the contrast of colors in the app, as well as an option to invert the colors. Additionally, you can provide text labels to accompany any images or graphics, ensuring that they are always understood.
What is nil coalessing in iOS engineering?
Nil coalescing is a short-hand operator used in Swift programming to simplify the process of unwrapping optionals. It allows developers to check if a value is nil and, if so, use a default value instead. It is written in the form of “a ?? b” and will return the value of a if it is not nil, otherwise it will return the value of b.
What tools can we use for CI/CD in iOS engineering?
1. Fastlane
2. Jenkins
3. Travis CI
4. CircleCI
5. Bitrise
6. AppCenter
7. BuddyBuild
8. CodeShip
9. Bamboo
10. Xcode Server
Can you briefly explain each?
1. Fastlane: Fastlane is an open source project designed to automate mobile app development and deployment. It automates the process of building, testing, and deploying iOS, Android and web apps, allowing developers to focus more on the code.
2. Jenkins: Jenkins is an open source continuous integration and continuous delivery platform. It automates the process of building, testing, and deploying iOS and Android projects.
3. Travis CI: Travis CI is an open source continuous integration platform for iOS and Android. It automates the process of building, testing, and deploying applications.
4. CircleCI: CircleCI is a continuous integration and continuous delivery platform for iOS and Android. It automates the process of building, testing, and deploying applications.
5. Bitrise: Bitrise is a continuous integration and continuous delivery platform for iOS and Android. It automates the process of building, testing, and deploying applications.
6. AppCenter: AppCenter is an open source continuous integration and continuous delivery platform for iOS and Android. It automates the process of building, testing, and deploying applications.
7. BuddyBuild: BuddyBuild is a continuous integration and delivery platform for iOS and Android. It automates the process of building, testing, and deploying applications.
I thought BuddyBuild was acquired my Apple?
Yes, it is true that Apple acquired Buddy Build in 2018. Buddy Build is a mobile development platform that allows developers to easily create, test, and deploy mobile apps for iOS and Android.
is BuddyBuild still available?
Yes, Buddy Build is still available. However, as of March 2019, it is no longer open to new customers. Apple is now using Buddy Build internally to develop and test their own applications.