Dependency injection in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a protocol for dependency injection.

iOS Swift

protocol [1] {
  func fetchData() -> String
}

Drag options to blanks, or click blank then click option'

ADataService

BInjectable

CDependency

DServiceProtocol

Attempts:

3 left

💡 Hint

Common Mistakes

Using a class name instead of a protocol name

Using vague names like 'Dependency'

The protocol defines the contract for the service. Naming it ServiceProtocol clearly indicates its role.

2fill in blank

medium

Complete the code to inject a dependency via initializer.

iOS Swift

class ViewModel {
  let service: ServiceProtocol

  init([1]: ServiceProtocol) {
    self.service = service
  }
}

Drag options to blanks, or click blank then click option'

AserviceProtocol

Bdependency

Cservice

DdataService

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name that confuses the assignment

Forgetting to assign the parameter to the property

The parameter name service matches the property and type, making the code clear and consistent.

3fill in blank

hard

Fix the error in the code by completing the injection of a mock service.

iOS Swift

class MockService: [1] {
  func fetchData() -> String {
    return "Mock Data"
  }
}

Drag options to blanks, or click blank then click option'

AService

BServiceProtocol

CInjectable

DDataService

Attempts:

3 left

💡 Hint

Common Mistakes

Conforming to a class instead of a protocol

Using incorrect protocol names

The mock class must conform to the ServiceProtocol to be used as a dependency.

4fill in blank

hard

Fill both blanks to create a property and assign it in the initializer for dependency injection.

iOS Swift

class Controller {
  private let [1]: ServiceProtocol

  init([2]: ServiceProtocol) {
    self.service = service
  }
}

Drag options to blanks, or click blank then click option'

Aservice

Bdependency

DdataService

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for property and parameter

Using vague names like 'dependency'

The property and initializer parameter should both be named service to keep the code clear and consistent.

5fill in blank

hard

Fill all three blanks to complete a function that uses dependency injection to fetch data.

iOS Swift

func displayData(using [1]: [2]) -> String {
  return [3].fetchData()
}

Drag options to blanks, or click blank then click option'

Aservice

BServiceProtocol

DdataService

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching parameter name and usage

Using incorrect protocol or variable names

The function parameter name is service of type ServiceProtocol, and the method calls service.fetchData().