Koin-style Dependency Injection

1import org.koin.core.module.dsl.*
2import org.koin.dsl.*
3import org.koin.core.component.*
4import org.koin.core.context.*
5 
6interface UserRepository {
7    fun findById(id: Int): User?
8    fun save(user: User): User
9}
10 
11class UserRepositoryImpl : UserRepository {
12    private val users = mutableMapOf<Int, User>()
13    
14    override fun findById(id: Int) = users[id]
15    override fun save(user: User) = user.also { users[it.id] = it }
16}
17 
18class UserService(private val repository: UserRepository) {
19    fun getUser(id: Int) = repository.findById(id)
20    fun createUser(name: String, email: String): User {
21        val user = User(users.size + 1, name, email)
22        return repository.save(user)
23    }
24}
25 
26val appModule = module {
27    singleOf(::UserRepositoryImpl) { bind<UserRepository>() }
28    singleOf(::UserService)
29}
30 
31class MyApplication : KoinComponent {
32    private val userService: UserService by inject()
33    
34    fun run() {
35        val user = userService.createUser("Alice", "alice@example.com")
36        println("Created: ${user.name}")
37    }
38}