Use cases / Interactors in Android Kotlin

Introduction

Use cases help organize app actions clearly. They keep your app's logic simple and easy to change.

When you want to separate app logic from the user interface.

When you need to reuse the same action in different parts of your app.

When you want to make your app easier to test.

When your app has multiple steps or rules for a task.

When you want to keep your code clean and organized.

Syntax

Android Kotlin

class SomeUseCase {
  fun execute(param: Type): ResultType {
    // business logic here
    return result
  }
}

Use cases are simple classes with one main function, often called execute.

They focus on one task or action your app does.

Examples

This use case checks if login details are correct.

Android Kotlin

class LoginUseCase {
  fun execute(username: String, password: String): Boolean {
    return username == "user" && password == "pass"
  }
}

This use case returns a list of items.

Android Kotlin

class FetchItemsUseCase {
  fun execute(): List<String> {
    return listOf("Apple", "Banana", "Cherry")
  }
}

Sample App

This program creates a use case to add two numbers. It then runs it and prints the result.

Android Kotlin

class AddNumbersUseCase {
  fun execute(a: Int, b: Int): Int {
    return a + b
  }
}

fun main() {
  val useCase = AddNumbersUseCase()
  val result = useCase.execute(3, 4)
  println("Sum is: $result")
}

Important Notes

Use cases keep your app logic in one place, making it easier to update.

They help you write tests for your app actions without the UI.

Keep use cases focused on one job for clarity.

Summary

Use cases organize app actions clearly and simply.

They separate logic from the user interface.

Use cases make your app easier to test and maintain.