simple-di.kt

// Sample from http://www.pacoworks.com/2018/02/25/simple-dependency-injection-in-kotlin-part-1/

interface DaoDatabase {
    fun query(s: String): Any
}

class User(val id: Int)

interface DaoOperationsSyntax {
    val dao: DaoDatabase

    fun User.queryUser() =
            dao.query("SELECT * from Users where userId = ${this.id}")
}

object DataRepository {
    fun DaoOperationsSyntax.getUser(user: User) = user.queryUser()
}


fun main(args: Array<String>) {

    val mySyntax = object : DaoOperationsSyntax {
        override val dao: DaoDatabase = object : DaoDatabase {
            override fun query(s: String): Any = TODO()
        }

        override fun User.queryUser(): Any {
            return "Test"
        }
    }

    println(mySyntax.getUser(User(1))) // prints Test
}