Growth Path from Entry Level to Intermediate iOS Developer

As you evolve from a junior iOS developer, you enter what I like to call the “growth zone” – that sweet spot where you’re no longer struggling with the basics but aren’t yet shouldering the full responsibilities of a senior developer. This mid-level phase is crucial for your career development and often determines how quickly you’ll advance to more senior positions.

Advanced Swift Concepts

By now, you should be comfortable with Swift basics, but mid-level developers need to go deeper:

Protocol-Oriented Programming: Understanding how to leverage protocols for flexible, modular code design
Generics: Creating reusable components that work with any type while maintaining type safety
Functional Programming: Using map, filter, reduce, and higher-order functions to write cleaner, more expressive code
Swift Concurrency: Familiarity with async/await, actors, and structured concurrency

PROJECT IDEA: Protocol-Based Image Loading System

Create a small app that implements a flexible image loading system using protocols and generics. Build an ImageLoadable protocol with different implementations (network, cache, local) and use generics to handle different image processing options. This project will reinforce protocol-oriented programming and generics in a practical context.

PROJECT IDEA: Custom Result Builder

Create a small utility that uses Swift’s result builder feature to construct a complex object graph in a declarative way. For example, build a form validation system where you can define validation rules using a custom DSL. This will deepen your understanding of Swift’s more advanced type system features.

Architecture & Design Patterns

Mid-level developers should understand various architectural approaches:

MVVM (Model-View-ViewModel): Separating UI logic from business logic
Coordinator Pattern: Managing navigation flow independently from view controllers
Repository Pattern: Abstracting data sources behind a clean interface
Dependency Injection: Providing dependencies rather than creating them internally
VIPER: Breaking applications into View, Interactor, Presenter, Entity, and Router components for highly modular code
Clean Architecture: Implementing clear boundaries between layers with domain-centric design
Modular Architecture: Structuring your app into independent, reusable modules that can be developed and tested in isolation

You should be able to explain the tradeoffs between different patterns and know when to apply each one. For example, MVVM works great for complex view logic, but might be overkill for simple screens. I’ve found that mixing patterns pragmatically rather than dogmatically following one approach leads to better codebases.

When I review code from junior developers, I often see massive view controllers handling everything from networking to UI updates. As a mid-level developer, you should be breaking these responsibilities apart using appropriate patterns.

PROJECT IDEA: Task Manager with MVVM + Coordinator

Build a simple task management app using MVVM architecture with a Coordinator pattern for navigation. Include different task categories and priority levels. This project will help you practice separating concerns and managing navigation flow independently from your view controllers.

PROJECT IDEA: Feature Flags Implementation

Build a reusable feature flag system that allows enabling/disabling features remotely. Implement different strategies (local config, remote config, user segmentation) and design it to be easily integrated into any app. This project will reinforce dependency injection and strategy pattern concepts.

State Management

As apps grow more complex, state management becomes critical:

Reactive Programming: Using Combine (or RxSwift) to manage asynchronous events
Unidirectional Data Flow: Understanding concepts like Redux or The Composable Architecture where data flows in one direction, making state changes predictable and traceable
State Containers: Creating predictable state management systems
UI Updates vs. Background Processing: Knowing how to properly separate UI updates on the main thread from intensive processing work on background threads
Source of Truth: Establishing clear ownership of data to prevent inconsistencies and race conditions

State management is one of those skills that separates mid-level developers from beginners. I remember the first time I implemented a proper state management system – suddenly bugs related to inconsistent UI states virtually disappeared.

A good mid-level iOS developer can explain how state flows through their application and has strategies for keeping that state consistent across multiple screens and throughout the app’s lifecycle.

PROJECT IDEA: Weather App with Unidirectional Data Flow

Create a weather app that implements a Redux-like state management system. All state changes (location updates, weather data fetching, unit conversions) should flow through a central store with reducers. This will demonstrate how predictable state management simplifies complex UI updates.

PROJECT IDEA: Multi-User Drawing App with State Synchronization

Create a collaborative drawing app where multiple users can draw on the same canvas. Focus on state synchronization challenges and conflict resolution. This project will help you understand complex state management in a real-time collaborative environment.

Performance & Optimization

Memory issues can make or break your app:

ARC (Automatic Reference Counting): Deep understanding of how Swift manages memory
Retain Cycles: Identifying and preventing memory leaks
Value vs. Reference Types: Knowing when to use each for optimal performance

Instruments: You should be comfortable with Memory Graph Debugger to visualize object relationships and the Allocations instrument to track memory growth over time. I use these tools regularly to ensure my apps don’t consume excessive memory.

Concurrency

Modern apps require efficient background processing:

Grand Central Dispatch (GCD): Beyond just using DispatchQueue.main, you should understand queue types (serial vs. concurrent), quality of service levels, and work item flags. I often create custom queues for specific subsystems in my apps.
Operations and OperationQueues: These provide more control than raw GCD, with support for cancellation, dependencies, and priorities. I use operations for complex tasks like image processing pipelines where I need to manage task relationships.
Thread Safety: You should know how to protect shared resources using locks, serial queues, or the newer actor type in Swift. Race conditions are among the hardest bugs to track down, so I always design with thread safety in mind.
Async/await: Swift’s structured concurrency model simplifies asynchronous code. You should understand task groups, continuations, and how to migrate from completion handler-based code to the new syntax.
UI Updates: Ensuring smooth user experience while performing background work

App Performance

Users expect snappy, responsive apps:

Table/Collection View Optimization: You should pre-calculate cell heights, reuse cells properly, and implement prefetching to maintain smooth scrolling. I’ve seen dramatic performance improvements by moving image processing off the main thread and caching results.
Image Loading and Caching: Implement proper image caching and downsampling to avoid excessive memory use. I typically use a third-party library or build a custom solution that loads appropriately sized images rather than scaling them at render time.
Launch Time Optimization: Use Instruments’ Time Profiler to identify slow code paths during app launch. I’ve reduced launch times by deferring non-critical initialization and using background loading for resources.
Battery Efficiency: Batch network requests, use push notifications instead of polling, and optimize location updates to preserve battery life. Your users will thank you for an app that doesn’t drain their battery.
Rendering Performance: Understand Core Animation’s rendering pipeline and how to avoid expensive drawing operations. I use the Core Animation instrument to identify dropped frames and optimize layer properties for hardware acceleration.

PROJECT IDEA: Image Gallery with Performance Optimizations

Build an infinite-scrolling image gallery that implements proper cell reuse, image caching, and background image processing. Use Instruments to measure and optimize your implementation. The goal is to maintain 60fps scrolling even with high-resolution images.

PROJECT IDEA: Video Processing Pipeline

Build a video processing app that applies filters to videos while maintaining smooth playback. Implement frame caching, background processing, and progress reporting. Use Instruments to identify and resolve bottlenecks. This will teach you advanced performance optimization techniques with large media files.

Networking & Data

API Integration

Most apps need to communicate with backend services:

URLSession: Going beyond basic requests to handle authentication, caching, etc. I recommend creating a dedicated networking layer that abstracts URLSession complexity. You should understand how to configure session tasks with different configurations and handle authentication tokens properly.
JSON Parsing: Using Codable effectively for serialization/deserialization. At this level, you should be comfortable with custom coding keys, date formatting strategies, and handling nested optional structures. I’ve found creating dedicated decoder factories with pre-configured settings improves code reusability.
API Design: Understanding RESTful principles and other API paradigms like GraphQL. You should be able to design client-side models that efficiently map to your backend services. I recommend creating clear separation between API models and domain models in your app.
Error Handling: Creating robust network layers that gracefully handle failures. You should implement proper error types that distinguish between network failures, server errors, and parsing issues. I always ensure my network layer provides meaningful error messages that can be appropriately displayed to users.
Offline Support: Implementing strategies for offline-first experiences. This includes request queuing, conflict resolution, and synchronization patterns. I’ve found that users appreciate apps that work seamlessly regardless of connection status.

PROJECT IDEA: Robust File Download Manager

Create a download manager that handles large file downloads with pause/resume capability, bandwidth throttling, and automatic retry on failure. Implement background downloads that continue when the app isn’t active. This project will teach you advanced URLSession techniques and proper error recovery.

Persistence

Data storage is fundamental to most applications:

Core Data: Moving beyond basics to relationships, migrations, and performance optimization. You should understand fetch request templates, batch processing, and background contexts. I regularly use NSFetchedResultsController to efficiently drive UI from persistent stores.
UserDefaults: Proper usage for preferences and small data. You should wrap UserDefaults access in dedicated types with type-safe property wrappers. I avoid storing sensitive information here and respect data size limitations.
FileManager: Efficiently working with the file system for document storage, caching, and temporary files. You should understand iOS sandbox directories and their appropriate uses. I always implement proper error handling for file operations.
CloudKit/Firebase: Understanding cloud storage options for syncing user data across devices. You should be familiar with subscription models, zones, and record types. I’ve found implementing proper conflict resolution strategies is critical for multi-device apps.
Database Alternatives: Familiarity with options like Realm, SQLite, or GRDB for cases where Core Data isn’t ideal. You should understand the tradeoffs between different persistence solutions. I select storage technologies based on specific app requirements rather than defaulting to one solution.
Data Migration: Implementing strategies for migrating data between app versions. You should be comfortable with lightweight and heavyweight Core Data migrations, as well as custom migration paths. I always thoroughly test migration paths before releasing updates.

PROJECT IDEA: Offline-First News Reader

Create a news reader app that works seamlessly offline. Implement a robust networking layer with proper error handling, and use Core Data to cache articles. Add synchronization logic that queues user actions (like bookmarks or comments) when offline and syncs when connectivity returns.

Testing & Quality

Mid-level developers should write testable code:

XCTest Framework: Beyond just knowing how to create a test, you should understand test lifecycle methods like setUp() and tearDown(), as well as performance testing with measure(). I always organize my tests using descriptive naming that clearly indicates what’s being tested and the expected outcome.
Test Doubles: You should be comfortable creating and using mocks, stubs, and fakes to isolate the code you’re testing. I find protocol-based mocking particularly powerful in Swift – by having your dependencies conform to protocols, you can easily swap in test doubles. For example, replacing a network service with a mock that returns predefined responses without making actual network calls.
Test Coverage: While 100% coverage isn’t always necessary, you should strategically test the most critical and complex parts of your codebase. I focus on testing business logic, edge cases, and regression-prone areas rather than simple property setters.
Testable Architecture: You should design your code with testing in mind, using dependency injection and proper separation of concerns. I’ve found that code that’s difficult to test is often poorly designed – testing challenges can highlight architectural issues.

PROJECT IDEA: Testable Authentication Module

Develop an authentication module with comprehensive unit tests. Include tests for successful login/signup flows as well as various error conditions. Use test doubles to simulate network responses and practice writing testable code with dependency injection.

PROJECT IDEA: Snapshot Testing UI Component Library

Develop a small UI component library with comprehensive snapshot tests. Include tests for different device sizes, dark/light mode, and accessibility settings. This will teach you how to ensure visual consistency across app updates and different environments.

Debugging

Efficient debugging saves countless hours:

LLDB: You should go beyond basic po commands to leverage the full power of LLDB. I regularly use commands like expression to modify variables at runtime, watchpoint set to pause execution when a variable changes, and custom LLDB commands to streamline repetitive debugging tasks.
Breakpoints: Master conditional breakpoints that only trigger when specific conditions are met, and action breakpoints that can log information or run scripts without pausing execution. I often add sound-playing actions to breakpoints in asynchronous code to alert me when they’re hit without interrupting program flow.
Crash Analysis: You should be able to interpret crash logs, symbolicate them if needed, and trace the execution path that led to the crash. I’ve developed a systematic approach to crash debugging that starts with reproducing the issue, then examining the stack trace to identify the failure point.
Network Debugging: Tools like Charles Proxy or Proxyman should be part of your toolkit for inspecting network traffic. I use these to verify request/response data, simulate poor network conditions, and mock API responses during development. Understanding HTTP status codes, headers, and common authentication schemes is essential for effective network debugging.
Memory Debugging: You should be proficient with Instruments’ Leaks and Allocations tools to identify memory issues. I regularly check for retain cycles by using the Memory Graph Debugger and adding strategic logging of deinitialization to confirm objects are being released when expected.
Time Profiling: Understanding how to use Instruments’ Time Profiler to identify performance bottlenecks. I look for functions consuming excessive CPU time and optimize hot paths in the code.

Remember that debugging is as much about prevention as it is about fixing issues. As a mid-level developer, you should be building logging systems, error reporting, and monitoring into your apps from the start, making future debugging sessions more productive.

UI/UX Implementation

Advanced UI Components

Moving beyond basic controls:

Custom Views: Creating reusable, flexible UI components that encapsulate both appearance and behavior. I always start by subclassing UIView and implementing init(frame:) and init(coder:), then add custom properties with proper invalidation of layout when they change. Remember to override layoutSubviews() for custom layout logic rather than doing layout in init.
Animations: Adding polish with Core Animation and UIView animations. You should understand animation curves, timing functions, and how to chain animations together. I often use UIViewPropertyAnimator for interruptible animations and layer animations for more complex effects. Don’t forget about UISpringTimingParameters for natural-feeling bounce effects.
Adaptive Layouts: Supporting different screen sizes and orientations using Auto Layout, size classes, and trait collections. I recommend creating extension methods that configure constraints programmatically for reusability. Understanding layout priorities and compression resistance is crucial for complex UIs that need to adapt gracefully.
Accessibility: Making your app usable by everyone through proper VoiceOver support, Dynamic Type, and sufficient color contrast. I always test my apps with VoiceOver enabled and ensure all interactive elements have meaningful accessibility labels. Remember that supporting accessibility isn’t optional—it’s essential for creating truly inclusive apps.
Gesture Recognizers: Implementing custom gestures beyond taps, like pan, pinch, and rotation. You should understand how to combine gestures and handle gesture state transitions. I often create custom gesture recognizer subclasses for complex interactions.

Design Systems

Understanding the bigger picture:

Component Libraries: Building and maintaining UI component systems that ensure consistency across your app. I typically create a centralized design system module that other features can import. Your components should be highly configurable while maintaining design consistency.
Style Guides: Implementing consistent visual languages through color palettes, typography, and spacing systems. I recommend creating extensions on UIColor and UIFont that provide semantic access to your design tokens (e.g., UIColor.primaryBackground instead of hard-coded colors).
Design-to-Code Translation: Effectively turning designs into working interfaces while maintaining the design intent. You should be comfortable discussing implementation trade-offs with designers and suggesting alternatives when designs are technically challenging.
Theming: Implementing support for light/dark mode, custom brand themes, or user-selectable themes. I use a combination of asset catalogs with appearances and programmatic styling to achieve flexible theming.

PROJECT IDEA: Custom Control Library

Build a small library of 3-5 custom UI controls (like a rating selector, expandable text field, or customizable progress indicator). Make them highly configurable, adaptive to different screen sizes, and fully accessible. Package them as a reusable module with a demo app showcasing their capabilities.

Modern UI Paradigms

Staying current with evolving UI patterns:

SwiftUI Integration: Understanding how to integrate SwiftUI views into UIKit applications and vice versa. I often use SwiftUI for simpler UI components while maintaining UIKit for more complex interactions.
Compositional Layouts: Leveraging UICollectionViewCompositionalLayout for complex, responsive grid layouts. This API makes previously challenging layouts straightforward to implement.
Diffable Data Sources: Using modern table and collection view data sources for smooth animations when data changes. I’ve found this approach eliminates many common bugs related to data source updates.
Context Menus: Implementing contextual actions through long-press menus. These provide powerful functionality without cluttering your UI.

PROJECT IDEA: Interactive Onboarding Experience

Build an onboarding flow with interactive tutorials that teach users how to use app features. Implement animations, gestures, and guided tours that respond to user actions. This project will help you create more engaging and instructive user experiences.

PROJECT IDEA: Custom Transition Library

Create a library of custom view controller transitions that can be easily applied to any app. Include interactive transitions that respond to gestures and transitions that adapt to different presentation contexts. This will deepen your understanding of UIKit’s view controller presentation system.

Soft Skills for Mid-Level Developers

Technical skills are only part of the equation. As a mid-level developer, you also need to develop these soft skills:

Communication

Being able to explain technical concepts clearly to both technical and non-technical team members is invaluable. I’ve found that the ability to translate complex ideas into simple terms has helped me collaborate more effectively with designers and product managers.

Time Management

As you take on more responsibility, you’ll need to manage your time efficiently. I use the Pomodoro Technique (25 minutes of focused work followed by a 5-minute break) to maintain productivity throughout the day.

Problem-Solving Approach

Develop a systematic approach to debugging and problem-solving. When I encounter a difficult bug, I follow these steps:

Reproduce the issue consistently
Isolate the problem area
Form a hypothesis about the cause
Test the hypothesis
Implement and verify the solution

Mentoring Junior Developers

Even as a mid-level developer, you can start mentoring those with less experience. I’ve found that teaching others has deepened my own understanding of iOS development concepts.

Staying Current

The iOS ecosystem evolves rapidly. Mid-level developers should:

Follow Apple’s Developments: Watching WWDC sessions and implementing new frameworks
Community Engagement: Reading blogs, participating in forums, attending meetups
Continuous Learning: Exploring adjacent technologies that complement iOS development

PROJECT IDEA: Framework Exploration App

Create a simple app that implements a framework or API introduced in the most recent version of iOS. Document your learning process in comments or a companion blog post. This project will keep you current with Apple’s latest technologies while building your technical writing skills.

Resources for Growth

To accelerate your journey to intermediate level, I recommend these resources:

Swift

SwiftUI

Combine

Multithreading

Concurrency by Tutorials by Scott Grosch

Database

Architecture

macOS

App Distribution

iOS App Distribution & Best Practices by Keegan Rush, Pietro Rea

Interview

Conclusion

The mid-level phase of your iOS development career is all about deepening your technical expertise while broadening your understanding of the entire development process. It’s not just about writing code that works—it’s about writing code that’s maintainable, performant, and aligned with business goals.

I remember when I first started tackling these mid-level skills, it felt overwhelming. But take it one step at a time, focus on real-world applications of these concepts, and you’ll find yourself naturally progressing toward senior-level expertise.

What mid-level skills are you currently working on? Drop a comment below, and let’s discuss your iOS development journey!