iOS-Developer-and-Designer-Interview-Questions

A small guide to help those looking to hire a developer or designer for iOS work. While tailored for iOS, many questions could be used for Android developers or designers as well. A great self-test if you're looking to keep current or practice for your own interview.

Inspired by the wonderful Front-end Job Interview Questions, I've done my best to match their format and have pulled some of their best questions for inclusion here. Pull requests and suggestions to this repository are highly encouraged.

Contributors: Original work by Cameron Banga. Big thanks to Joe Pasqualetti for his significant additions here so far!

Table of Contents

1. General Questions
2. iOS Technologies Questions
3. Coding Questions
4. Interface Questions
5. Design Questions
6. App Store Questions
7. Fun Questions
8. Other References
9. License

####[⬆] General Questions:

• What did you learn yesterday/this week?
• What excites or interests you about making software?
• Which version control systems are you familiar with?
• Do you have experience working with projects on GitHub?
• Do you contribute to any iOS open source projects on GitHub or a similar site?
• Can you describe your workflow when you work on creating an iOS app?
• Are you familiar with CocoaPods? Can you explain what they are and how they work?
• In general, explain software licensing and how this applies to work we do.
• Describe your general testing practices when building an iOS app.
• How can apps support other languages, date formats and currencies?
• What is Instruments and how is it useful?

####[⬆] iOS Technologies Questions:

• Explain Handoff, and in general, how it it allows iOS and Mac/web apps to communicate?
• What technologies/services are contained inside of iCloud?
• What is an iOS extension? Can you list a few examples of popular/common extensions?
• What is HealthKit?
• What is HomeKit?
• What is Apple Pay? Could you describe a way we could use it in our applications?
• Explain application sandboxing.
• What is VoiceOver? Explain some of the accessibility features included in iOS and how developers can utilize them.
• How does application multitasking work on iOS?
• What features does Game Center offer for iOS games?
• What are iBeacons?
• What is Cocoa/Cocoa Touch?
• Explain in general, what Core Audio, Core Data, and Core Location are, and how they help iOS apps.
• Describe the role of SpriteKit and SceneKit.
• What is Metal?
• What is the responder chain? How does it work?
• What are the different actions that buttons and other controls can respond to?
• What is the role of the application delegate?
• Explain NSUserDefaults. How would you serialize an array to disk?
• How would you store user's credentials?
• Explain Keychain Services.
• Why are caching and compression important on mobile devices?
• Explain ~/Documents, ~/Library, ~/tmp. What directory is ~ on iOS?
• How does AirPlay work? How would you use it (programmatically) to enhance the utility and presentation of an app?
• Give a brief overview of what sensors, IO and communication methods (Wifi, telephony, etc) are available on iOS. How can you make use of these?
• What are the hardware performance differences among the iPad 2 / iPad mini 1-3, iPad Retina, iPad Air 2, iPhone 5, 5s, 6, and 6+. What do these constraints mean for performance intensive apps?

####[⬆] Coding Questions:

• What does Cocoa Touch include and not include?
• Why do Cocoa Touch classes start with two capital letters?
• What is Swift, what is Objective-C and how do they relate and compare?
• Explain why optionals are useful in Swift.
• Explain NSError and how it works (or doesn't) in Swift.
• How does instancetype work and how is it useful?
• When is let appropriate in Swift? var?
• Why and where is the map function useful.
• How do you track down bugs? What are your tools of choice?
• You found a bug in Cocoa. What do you do?
• There is a regression in a new distributed version of our app causing crashes. How do you mitigate it? How will you prevent new bugs from reaching customers?
• How are Objective-C classes implemented? Describe how the Objective-C runtime is implemented.
• What security does iOS offer to protect customers and privileged information?
• Our app downloads data and displays it immediately. In accordance with MVC where is the best place to perform the download?
• How does MVC influence the design of a codebase?
• What methods are part of the controller life-cycle? The view life-cycle?
• What design patterns does iOS make use of? What design patterns do you use in your codebase?
• What threads does iOS provide and how can you best utilize them?
• Give a brief description of how UIScrollView is implemented. How does it operate with gesture recognizers, multiple touches and the run loops?
• What API would you add or improve on iOS?

####[⬆] Interface Questions:

• What is the screen resolution of the iPhone 5, 6, 6+. and iPad Air 2?
• What units is the resolution measured in?
• Explain the purpose of Interface Builder, what is a NIB file?
• What image filetype should iOS UI assets be saved in?
• Describe some differences between a Storyboard and a standard NIB file.
• What is the device status bar? How tall is it in points? Is it opaque or transparent? What does it do during a phone call or navigation?
• What is a navigation bar? Can you show me an Apple app on your phone that uses a navigation bar?
• What is a tab bar? What is a toolbar? Compare and contrast them.
• What is a table view? What is a collection view?
• Describe when a popover is most appropriate.
• What is a split-view controller?
• What sort of content would be appropriate to place in a picker view?
• When are a label, text field and text view appropriate?
• What does a segmented control do?
• What is a modal view?
• What kind of notifications does iOS offer?

####[⬆] Design Questions:

• What is an iOS app icon? Describe it as best as you can.
• What is the smallest size an app icon could be? What's the largest size it could be?
• Can an app icon contain any transparency?
• How does a Newsstand icon differ from a regular app icon?
• Explain a launch image.
• Describe the purpose of Auto Layout, and in general, how it works.
• Describe the role of animation in design of software.
• Describe the role of interactivity and feedback when designing software.
• What are some differences to take into account when building an iPhone app vs an iPad app?
• Describe the importance and role of prototyping when working on an app design.

####[⬆] App Store Questions:

• How do In-App Purchases work? What can be purchased with IAP?
• Have you ever submitted an app to the App Store? Can you explain the general process?
• What is iTunes Connect?
• What is a provisioning profile?
• What is an App ID?
• What are the differences between Development and Production iOS signing certificates?
• How is TestFlight used? How were UUIDs used in ad-hoc app distribution?
• When do purchase receipts need to be verified?
• What is required to display iAds?

####[⬆] Fun Questions:

• What's a cool thing you've coded recently? What's something you've built that you're proud of?
• What are some things you like about the developer tools you use?
• Who are some of your favorite independent Mac or iOS developers?
• Do you have any pet projects? What kind?
• What would you change about Xcode?
• What is your favorite iOS API?
• Do you have a pet or favorite bug report?
• What are your favorite ways to investigate an new technology?
• Why are dictionaries called dictionaries? Why not hash tables or hash maps?

####[⬆] Other References:

• iOS Dev Weekly
• Accidental Tech Podcast
• Debug Podcast
• The Talk Show
• NSHipster
• KZBootstrap
• WWDC Videos
• ASCII WWDC
• Pttrns
• Ray Wenderlich Tutorials
• iOS Version Stats
• iOS Human Interface Guidelines
• Black Pixel blog post on hiring iOS and Mac engineers
• Macoscope guide to a technical interview

####[⬆] License:

Released under the MIT License. See LICENSE file for details.