diff --git a/core-kotlin/src/main/kotlin/com/baeldung/kotlin/delegates/InterfaceDelegation.kt b/core-kotlin/src/main/kotlin/com/baeldung/kotlin/delegates/InterfaceDelegation.kt new file mode 100644 index 0000000000..8e261aacf2 --- /dev/null +++ b/core-kotlin/src/main/kotlin/com/baeldung/kotlin/delegates/InterfaceDelegation.kt @@ -0,0 +1,64 @@ +package com.baeldung.kotlin.delegates + +import java.util.concurrent.locks.ReentrantLock +import kotlin.concurrent.withLock + +interface Producer { + + fun produce(): String +} + +class ProducerImpl : Producer { + + override fun produce() = "ProducerImpl" +} + +class EnhancedProducer(private val delegate: Producer) : Producer by delegate { + + override fun produce() = "${delegate.produce()} and EnhancedProducer" +} + +interface MessageService { + + fun processMessage(message: String): String +} + +class MessageServiceImpl : MessageService { + override fun processMessage(message: String): String { + return "MessageServiceImpl: $message" + } +} + +interface UserService { + + fun processUser(userId: String): String +} + +class UserServiceImpl : UserService { + + override fun processUser(userId: String): String { + return "UserServiceImpl: $userId" + } +} + +class CompositeService : UserService by UserServiceImpl(), MessageService by MessageServiceImpl() + +interface Service { + + val seed: Int + + fun serve(action: (Int) -> Unit) +} + +class ServiceImpl : Service { + + override val seed = 1 + + override fun serve(action: (Int) -> Unit) { + action(seed) + } +} + +class ServiceDecorator : Service by ServiceImpl() { + override val seed = 2 +} \ No newline at end of file diff --git a/core-kotlin/src/test/kotlin/com/baeldung/kotlin/delegates/InterfaceDelegationTest.kt b/core-kotlin/src/test/kotlin/com/baeldung/kotlin/delegates/InterfaceDelegationTest.kt new file mode 100644 index 0000000000..e65032acd4 --- /dev/null +++ b/core-kotlin/src/test/kotlin/com/baeldung/kotlin/delegates/InterfaceDelegationTest.kt @@ -0,0 +1,28 @@ +package com.baeldung.kotlin.delegates + +import org.assertj.core.api.Assertions.assertThat +import org.junit.Test + +class InterfaceDelegationTest { + + @Test + fun `when delegated implementation is used then it works as expected`() { + val producer = EnhancedProducer(ProducerImpl()) + assertThat(producer.produce()).isEqualTo("ProducerImpl and EnhancedProducer") + } + + @Test + fun `when composite delegation is used then it works as expected`() { + val service = CompositeService() + assertThat(service.processMessage("message")).isEqualTo("MessageServiceImpl: message") + assertThat(service.processUser("user")).isEqualTo("UserServiceImpl: user") + } + + @Test + fun `when decoration is used then delegate knows nothing about it`() { + val service = ServiceDecorator() + service.serve { + assertThat(it).isEqualTo(1) + } + } +} \ No newline at end of file