Why clean architecture maintains codebases in iOS Swift - Build It to Prove It

Build: Clean Architecture Info

This screen explains why clean architecture helps keep codebases easy to maintain and grow.

Target UI

-----------------------------
| Clean Architecture Info   |
|---------------------------|
| Why use clean architecture?|
|                           |
| - Separates code clearly   |
| - Makes testing easier     |
| - Helps add features fast |
| - Keeps bugs low          |
|                           |
| [Close]                   |
-----------------------------

Show a title at the top

Display a bullet list explaining benefits of clean architecture

Add a Close button at the bottom that dismisses the screen

Starter Code

iOS Swift

import SwiftUI

struct CleanArchitectureInfoView: View {
    var body: some View {
        VStack {
            // TODO: Add title text here
            // TODO: Add bullet list here
            Spacer()
            // TODO: Add Close button here
        }
        .padding()
    }
}

struct CleanArchitectureInfoView_Previews: PreviewProvider {
    static var previews: some View {
        CleanArchitectureInfoView()
    }
}

Task 1

Task 2

Task 3

Task 4

Task 5

Task 6

Task 7

Solution

iOS Swift

import SwiftUI

struct CleanArchitectureInfoView: View {
    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            Text("Why use clean architecture?")
                .font(.title2)
                .bold()

            VStack(alignment: .leading, spacing: 8) {
                Text("- Separates code clearly")
                Text("- Makes testing easier")
                Text("- Helps add features fast")
                Text("- Keeps bugs low")
            }

            Spacer()

            Button(action: {
                print("Close tapped")
            }) {
                Text("Close")
                    .frame(maxWidth: .infinity)
                    .padding()
                    .background(Color.blue)
                    .foregroundColor(.white)
                    .cornerRadius(8)
            }
        }
        .padding()
    }
}

struct CleanArchitectureInfoView_Previews: PreviewProvider {
    static var previews: some View {
        CleanArchitectureInfoView()
    }
}

This screen uses a vertical stack to arrange the title, bullet points, and a Close button.

The title uses a bold, larger font to stand out.

The bullet points are simple Text views with a dash to simulate bullets, spaced nicely.

The Close button is styled with a blue background and white text, filling the width for easy tapping.

When tapped, it prints a message to the console to simulate closing the screen.

This simple layout clearly communicates why clean architecture helps maintain codebases by separating concerns, easing testing, speeding feature addition, and reducing bugs.

Final Result

Completed Screen

-----------------------------
| Clean Architecture Info   |
|---------------------------|
| Why use clean architecture?|
|                           |
| - Separates code clearly   |
| - Makes testing easier     |
| - Helps add features fast |
| - Keeps bugs low          |
|                           |
| [       Close Button      ]|
-----------------------------

User taps the Close button

Console prints 'Close tapped' to simulate closing the screen

Stretch Goal

Add a dark mode color scheme that changes background and text colors

💡 Hint

Use ColorScheme environment and conditional colors for background and text

Practice

1. Why does clean architecture help maintain large iOS codebases?

easy

A. It separates code into layers with clear responsibilities.

B. It combines all code into one file for simplicity.

C. It removes all comments to reduce clutter.

D. It uses only one programming language.

Solution

1. Step 1: Understand the role of layers in clean architecture

   Clean architecture divides code into layers, each with a specific job, like UI, business logic, and data.

2. Step 2: Recognize how separation aids maintenance

   This separation keeps code organized and easier to change without affecting unrelated parts.

3. Final Answer:

   It separates code into layers with clear responsibilities. -> Option A

4. Quick Check:

   Layered code = easier maintenance [OK]

Hint: Think: separate jobs make code easier to manage [OK]

Common Mistakes:

• Thinking all code in one file is simpler
• Believing removing comments improves maintenance
• Assuming language choice affects architecture

2. Which Swift code snippet best shows separation of concerns in clean architecture?

easy

A. struct User { var name: String } // Model
class UserView { func display() {} } // View
class UserService { func fetch() {} } // Service

B. class User { var name: String; func display() {} func fetch() {} }

C. var name = "User"; func display() { print(name) }

D. struct UserView { var name: String; func fetch() {} }

Solution

1. Step 1: Identify separation of concerns

   struct User { var name: String } // Model class UserView { func display() {} } // View class UserService { func fetch() {} } // Service splits code into Model, View, and Service classes, each with a clear job.

2. Step 2: Compare with other options

   Other options mix responsibilities in one class or struct, breaking separation.

3. Final Answer:

   Separate Model, View, and Service classes. -> Option A

4. Quick Check:

   Separate classes = separation of concerns [OK]

Hint: Look for separate classes for data, UI, and logic [OK]

Common Mistakes:

• Mixing UI and data in one class
• Putting fetch logic inside view structs
• Ignoring separation in code structure

3. Given this Swift code snippet, what is the main benefit of using clean architecture here?

protocol UserRepository {
  func getUser() -> User
}

class UserInteractor {
  let repo: UserRepository
  init(repo: UserRepository) { self.repo = repo }
  func fetchUser() -> User { repo.getUser() }
}

medium

A. It tightly couples data fetching with UI code.

B. It makes the code run faster by combining layers.

C. It allows easy swapping of data sources without changing business logic.

D. It removes the need for protocols in Swift.

Solution

1. Step 1: Analyze the use of protocol and interactor

   The protocol defines a contract for data fetching, and the interactor uses it without knowing details.

2. Step 2: Understand benefit of abstraction

   This abstraction allows changing data source (e.g., network or database) without changing business logic.

3. Final Answer:

   Allows easy swapping of data sources without changing business logic. -> Option C

4. Quick Check:

   Protocol abstraction = flexible data sources [OK]

Hint: Protocols hide details, making swapping easy [OK]

Common Mistakes:

• Thinking it couples UI and data tightly
• Assuming faster runtime from layering
• Believing protocols are unnecessary

4. Identify the problem in this Swift code violating clean architecture principles:

class UserViewController {
  func fetchUser() {
    let user = UserService().getUser()
    print(user.name)
  }
}

class UserService {
  func getUser() -> User { User(name: "Alice") }
}

medium

A. UserService should be a struct, not a class.

B. UserService should not return a User object.

C. UserViewController should not print user name.

D. UserViewController directly calls UserService, mixing UI and data logic.

Solution

1. Step 1: Check responsibility of UserViewController

   UserViewController is UI code and should not directly fetch data from service layer.

2. Step 2: Identify violation of separation

   Direct call to UserService mixes UI and data logic, breaking clean architecture.

3. Final Answer:

   UserViewController directly calls UserService, mixing UI and data logic. -> Option D

4. Quick Check:

   UI should not directly access data services [OK]

Hint: UI layer should not call data services directly [OK]

Common Mistakes:

• Thinking printing user name is wrong
• Believing UserService must be struct
• Assuming UserService can't return User

5. How does clean architecture help a team working on a large iOS app with many developers?

hard

A. By forcing all developers to write UI and data code together.

B. By dividing the app into layers, each team can focus on one layer without conflicts.

C. By removing the need for documentation and comments.

D. By making the app run only on one device type.

Solution

1. Step 1: Understand team collaboration challenges

   Large teams need clear boundaries to avoid conflicts and confusion.

2. Step 2: See how layering supports teamwork

   Clean architecture divides code into layers, so teams can work independently on UI, business logic, or data.

3. Final Answer:

   By dividing the app into layers, each team can focus on one layer without conflicts. -> Option B

4. Quick Check:

   Layered code = easier team collaboration [OK]

Hint: Layers let teams work separately without stepping on toes [OK]

Common Mistakes:

• Thinking all developers must write all code types
• Assuming documentation is unnecessary
• Believing architecture limits device support