Swift Best Practices for Writing Clean, Maintainable Code

Writing clean code that we can maintain is one of the most essential skills an iOS developer can develop. Swift is a versatile and expressive programming language, however, without organization and consistences, your code can become unreadable or extremely difficult to scale and debug. Following best practices, while building smaller features or large apps, will keep your projects organized, efficient, and maintainable.

In this article, we will go over the top Swift coding best practices that all developers should utilize to build clean and future-proof applications.

1. Use Meaningful and Consistent Naming Conventions.

Meaningful and descriptive naming, only require reading it to understand the code without additional comments.

Best Practices:

• Use variable and function names that describe their purpose.
• Keep clarity over conciseness.
• Use lowerCamelCase for variables and functions.
• Use UpperCamelCase for types, such as structs, classes, and enums.

For example: Use “calculateTotalPrice()” opposed to “calcTP()“.

Distinct naming will save you time, provide less confusion, while promoting code quality.

2. Keep Functions Small and Focused.

Large functions are difficult to test and debug. Swift encourages a clean and modular way of writing your code.

How do we do this?

• Limit functions to a singular responsibility.
• Divide large logic into smaller reusable methods.
• Use extensions to group functionality.

More reusable and focused methods result in easily maintainable code and the best way to limit complexity.

3. Use Optionals Safely / Avoid Forced Unwrapping

Swift’s optionals improve safety but can lead to runtime crashes if not used correctly.

Best Practices

• Use if let and guard let to safely unwrap
• Avoid using ! if you are not 100% sure the value exists
• Use optional chaining if appropriate

Good Example:
guard let user = user else { return }
Safe optional handling makes your app more stable and crash-resistant.

4. Use MVVM or another Clean Architecture Pattern

Architecture will define the maintainability of your entire app.

Patterns we recommend

• MVVM (Most common for SwiftUI and UIKit)
• MVC (Simple apps)
• VIPER (Enterprise worthy, modular apps)

A clean architecture will allow you to:

• Scale your application
• Reduce tight coupledness
• Testability

5. Use Structs by default and Classes when necessary.

Structs are value types and also provide immutability – thus generally make the code safer.

Use Structs When

• You don’t need to use inheritance
• The data structure is lightweight or immutable

Use Classes When

• You need reference semantics
• You need to use inheritance

Choosing the right type will reduce memory issues and make your code more predictable.

6. Avoid Massive View Controllers

One of the most common iOS issues is massive view controllers that take on too many responsibilities.

Use the following to fix problem:

• Extensions
• View models (MVVM)
• Service layers
• Separate file for all API calls, all formatting, and/or all business logic

Reducing the size of a view controller can greatly improve the cleanliness and maintainability of your code.

7. Utilize Protocols to Decrease Coupling

Protocols make your code more flexible, testable, and extensible.

Advantages

• Promotes dependency injection
• Facilitates mocking
• Simplifies unit testing
• Allows polymorphism without inheritance

Protocol-oriented programming is one of the best features of Swift.

8. Document Your Code Whenever Applicable

Commenting excessively is not essential, but strategic documentation will help future developers comprehend your intentions.

Guiding Principles

• Document difficult logic
• Leverage Swift’s native documentation syntax (///)
• Elucidate, do not describe

This will help facilitate comprehension as your project grows.

9. Keep Your Code DRY (Don’t Repeat Yourself)

Repetition leads to bugs and unnecessary maintenance.

How to Establish DRY

• Reuse shared logic throughout extensions, or utilities
• Offer shared helpers
• Refactor duplicate code into functions or protocols

The less duplicate code you write will minimize bugs and promote faster updates.

10. Use SwiftLint for Automatic Quality Control

SwiftLint will help ensure your coding standards across your project.

Benefits

• Provides consistent formatting
• Removes long code reviews for style bugs
• Improves long-term availability

Tools like SwiftLint turn high-quality Swift code into a no-brainer.

Final Remarks

Writing clean, maintainable Swift code is one of the most important things to create high-quality, scalable, and future-proof iOS applications. Adhering to these best practices—such as naming things meaningfully, using optionals safely, using a clean architecture, and keeping functions simple—ensures that your code is easier to read, debug and extend, among other things.

Whether you are a beginner or have years of experience as an iOS developer, adhering to these principles leads to cleaner code, fewer bugs, and easier development workflows.
Contact Us Today