Welcome to this **Koin Tutorial** for Android developers! In this step-by-step video, we’ll guide you through how to **set up a Repository and ViewModel using Koin** — a lightweight and powerful dependency injection (DI) framework made specifically for Kotlin.

If you're working with the **MVVM architecture** and want to learn how to manage dependencies in a clean, testable way, this tutorial is perfect for you. We’ll cover everything from configuring your `build.gradle` to injecting your `Repository` into a `ViewModel` using **Koin's DI magic**.

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### What You’ll Learn:

How to install and set up Koin in your Android project
How to create and inject a Repository using Koin
How to create a ViewModel and inject dependencies
How to define and load Koin modules
How to use ViewModel in Activities or Fragments

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### Prerequisites:

- Familiarity with Kotlin and Android Studio
- Basic understanding of MVVM architecture
- A working Android project to integrate Koin with

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### Tutorial Breakdown:

1. **Add Koin Dependencies** to your `build.gradle`:
```kotlin
implementation "io.insert-koin:koin-android:3.5.3"
implementation "io.insert-koin:koin-androidx-viewmodel:3.5.3"
```

2. **Create a Repository Class**:
```kotlin
class UserRepository {
fun getUser(): String = "John Doe"
}
```

3. **Create a ViewModel** and Inject the Repository:
```kotlin
class MainViewModel(private val userRepository: UserRepository) : ViewModel() {
fun getUsername(): String = userRepository.getUser()
}
```

4. **Define Your Koin Modules**:
```kotlin
val appModule = module {
single { UserRepository() }
viewModel { MainViewModel(get()) }
}
```

5. **Start Koin in Application Class**:
```kotlin
class MyApplication : Application() {
override fun onCreate() {
super.onCreate()
startKoin {
androidContext(this@MyApplication)
modules(appModule)
}
}
}
```

6. **Inject ViewModel in Activity/Fragment**:
```kotlin
class MainActivity : AppCompatActivity() {
private val mainViewModel: MainViewModel by viewModel()

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
println(mainViewModel.getUsername())
}
}
```

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### Bonus Tips:

- Koin’s `by viewModel()` makes injection seamless for Android components.
- Use `single` for shared instances and `factory` if you need new ones each time.
- Easily replace implementations for testing by swapping modules.

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