What iOS Engineers Actually Do
iOS engineers build the applications that users interact with on Apple devices. When you open an iPhone app, tap buttons, scroll through content, or receive a notification, iOS engineers designed and built those experiences. They bridge the gap between beautiful designs and functional software, working within Apple's strict guidelines while delivering smooth, responsive user experiences.
iOS Engineering vs. Mobile Engineering
A key hiring decision: should you hire iOS specialists or generalist mobile engineers?
When iOS Specialists Are Better
- Consumer-facing apps: iOS users spend more on apps and in-app purchases. A polished native experience directly impacts revenue.
- Complex iOS features: Camera processing, ARKit, HealthKit, or Watch integrations require deep platform expertise.
- Performance-critical apps: Games, video apps, and real-time features need native optimization.
- App Store optimization: Getting featured, managing reviews, and navigating Apple's policies requires specialized knowledge.
- Enterprise iOS deployment: MDM integration, security compliance, and corporate app distribution.
When Cross-Platform Might Work
- Smaller teams needing iOS and Android simultaneously
- Content-focused apps with simple interactions
- MVPs where speed to market outweighs platform optimization
- Internal tools where native polish is less critical
Swift vs. Objective-C: The Modern Landscape
Swift (Modern Standard)
Swift is Apple's modern programming language, introduced in 2014 and now the standard for iOS development. It's safer, more concise, and more performant than Objective-C.
What to look for:
- Swift 5+ experience (current stable version)
- Understanding of optionals, generics, and protocols
- Familiarity with Swift concurrency (async/await)
- Experience with Swift Package Manager
Objective-C (Legacy)
Objective-C was the primary iOS language for decades. Many large apps still have significant Objective-C codebases.
When Objective-C matters:
- Maintaining legacy codebases (banking, enterprise apps)
- Working with older C/C++ libraries
- Performance-critical code requiring manual memory control
Hiring guidance: Require Swift proficiency for all roles. Objective-C is a nice-to-have for roles involving legacy code, but shouldn't be a primary requirement unless your codebase is predominantly Objective-C.
SwiftUI vs. UIKit: The UI Framework Decision
UIKit (Established)
UIKit is Apple's mature UI framework with 15+ years of development. Most production apps use UIKit.
Strengths:
- Complete control over every UI element
- Extensive documentation and community resources
- Mature tooling and debugging support
- Supports all iOS versions
When to prefer UIKit experience:
- Apps supporting iOS 13 and earlier
- Complex custom UI requirements
- Large existing UIKit codebases
- Performance-critical interfaces
SwiftUI (Modern)
SwiftUI is Apple's declarative UI framework, introduced in 2019. It's the future of iOS development but still maturing.
Strengths:
- Faster development for standard interfaces
- Built-in accessibility and dark mode support
- Better cross-platform Apple development (iOS, macOS, watchOS)
- Less boilerplate code
When to prefer SwiftUI experience:
- New apps targeting iOS 15+
- Rapid prototyping needs
- Cross-platform Apple development
- Teams investing in Apple's future direction
Hiring guidance: Most iOS engineers should know UIKit well and have SwiftUI familiarity. For new apps targeting modern iOS versions, SwiftUI experience becomes more valuable. Don't require both at expert level—assess which matters more for your codebase.
Skills by Experience Level
Junior iOS Engineer (0-2 years)
Capabilities:
- Build standard iOS interfaces with UIKit or SwiftUI
- Implement basic networking and data persistence
- Follow existing architecture patterns
- Write unit tests for their code
- Navigate Xcode and debugging tools
Learning areas:
- Complex architecture patterns (MVVM, Coordinator)
- Performance optimization and profiling
- Memory management and leak detection
- App Store submission process
- Advanced iOS SDK features
Mid-Level iOS Engineer (2-5 years)
Capabilities:
- Design and implement features independently
- Architect moderate complexity applications
- Debug complex issues including crashes and memory leaks
- Review code and mentor juniors
- Handle App Store submissions and releases
Growing toward:
- System architecture decisions
- Cross-team technical leadership
- Performance optimization at scale
- Technical planning and estimation
Senior iOS Engineer (5+ years)
Capabilities:
- Architect complex applications from scratch
- Lead technical direction for mobile teams
- Optimize performance for challenging requirements
- Mentor and grow other engineers
- Drive technical strategy and tool choices
Demonstrates:
- Business impact awareness
- Cross-functional collaboration
- Technical decision documentation
- Platform expertise and Apple relationship
- Incident leadership and prevention
Curiosity & fundamentals
Independence & ownership
Architecture & leadership
Strategy & org impact
Where to Find iOS Engineers
High-Signal Sources
- GitHub: Contributors to popular iOS libraries (Alamofire, SnapKit, Realm)
- App Store: Engineers with shipped apps demonstrate real completion ability
- iOS communities: iOS Dev Weekly subscribers, Swift forums, CocoaHeads meetups
- Conference speakers: WWDC, try! Swift, iOS Conf SG presenters
- Apple certifications: While not required, they show commitment to the platform
Specialized Talent Pools
| Background | Strengths | Considerations |
|---|---|---|
| Big Tech iOS | Scale experience, code quality | May expect large team support |
| Agency iOS | Diverse project experience | Depth vs. breadth trade-off |
| Startup iOS | End-to-end ownership | May need process structure |
| Indie developers | Product sense, App Store savvy | Team collaboration experience |
Interview Focus Areas
Swift Fundamentals
"Explain the difference between structs and classes in Swift. When would you choose each?"
- Look for: Value vs. reference semantics, memory implications, protocol-oriented design thinking
- Red flag: Can't explain ARC or copy-on-write behavior
Architecture Understanding
"How would you structure a new iOS app? Walk me through your architecture decisions."
- Look for: Clear separation of concerns, testability considerations, practical trade-offs
- Red flag: Only knows one architecture pattern or can't explain why
Memory Management
"How do you identify and fix memory leaks in iOS applications?"
- Look for: Understanding of retain cycles, weak/unowned references, Instruments proficiency
- Red flag: Never dealt with memory issues, doesn't know debugging tools
Production Experience
"Tell me about a challenging bug you debugged in production."
- Look for: Systematic approach, use of crash reporting, handling of edge cases
- Red flag: Never worked on production apps
Common Hiring Mistakes
1. Requiring Both SwiftUI and UIKit Expertise
Expecting deep expertise in both frameworks is unrealistic for most candidates. Determine which matters more for your codebase and evaluate accordingly.
2. Ignoring App Store Experience
Many technically strong developers have never navigated App Store review, handled rejection feedback, or managed production releases. This experience matters for shipping.
3. Overweighting Algorithm Problems
LeetCode-style problems test general CS skills but not iOS engineering. Include iOS-specific challenges: debugging memory leaks, implementing custom UI components, or handling background tasks.
4. Neglecting Design Sense
iOS development is uniquely design-sensitive. Engineers who understand Apple's Human Interface Guidelines and care about polish create better user experiences. Ask about design decisions, not just technical ones.
5. Dismissing Indie Developers
Engineers who've shipped their own apps demonstrate product thinking, full-stack mobile skills, and completion ability. Don't overlook them because they lack big company experience.
Recruiter's Cheat Sheet
Resume Green Flags
- Apps in the App Store (especially with good reviews)
- Swift proficiency clearly stated
- Specific iOS frameworks mentioned (UIKit, SwiftUI, Core Data)
- Experience with CI/CD for iOS (Fastlane, Bitrise)
- Open source iOS contributions
- WWDC attendance or scholarship
- TestFlight and App Store Connect experience
Resume Yellow Flags
- Generic "mobile development" without iOS specifics
- Only cross-platform experience (React Native, Flutter)
- No shipped apps mentioned
- Objective-C only (unless legacy role)
- Missing iOS SDK specifics
- No mention of testing or quality practices
Technical Terms to Know
| Term | What It Means |
|---|---|
| Swift | Apple's modern programming language for iOS |
| UIKit | Traditional iOS UI framework (established) |
| SwiftUI | Modern declarative UI framework (newer) |
| Xcode | Apple's IDE for iOS development |
| CocoaPods/SPM | Dependency management tools |
| Core Data | Apple's data persistence framework |
| ARC | Automatic Reference Counting (memory management) |
| TestFlight | Apple's beta testing platform |
| App Store Connect | Apple's app management portal |
| MVVM/MVC | Architecture patterns (Model-View-ViewModel/Controller) |
| Instruments | Apple's profiling and debugging tool |
| HealthKit/ARKit | Specialized iOS frameworks for health data/augmented reality |
Developer Expectations
| Aspect | ✓ What They Expect | ✗ What Breaks Trust |
|---|---|---|
| Technical Environment | →Modern Mac hardware, latest Xcode, CI/CD pipeline (Fastlane or similar), and time to address technical debt. Access to real devices for testing, not just simulators. | ⚠Outdated Macs, forcing old Xcode versions, no CI/CD, or expecting quality without device testing. Telling them the codebase is "modern" when it's 90% Objective-C with no migration plan. |
| Codebase Quality | →Reasonable architecture, some test coverage, and a path to modernization if legacy code exists. Clear coding standards and code review process. | ⚠Massive view controllers, no architecture patterns, zero tests, and no acknowledgment that improvements are needed. Expecting them to "just ship features" without addressing quality. |
| Release Process | →Structured release process with TestFlight beta testing, reasonable review cycles, and engineer input on release timing. Understanding of App Store review requirements. | ⚠Chaotic releases, skipping beta testing, blaming engineers for App Store rejections, or pushing broken builds to production. Last-minute release demands without considering review times. |
| Growth and Learning | →WWDC attendance (or budget for videos/sessions), time to explore new iOS features, and path to senior/lead roles. Mentorship from experienced iOS engineers. | ⚠No learning budget, pressure to use outdated approaches, or dead-end role with no advancement. Being the only iOS engineer with no technical leadership support. |
| Design Collaboration | →Working relationship with designers who understand iOS patterns. Ability to push back on designs that violate Human Interface Guidelines or hurt performance. | ⚠Designs that ignore iOS conventions, no designer collaboration, or expectation to pixel-perfectly match Android regardless of platform differences. |