Advanced Object-Oriented Programming in Kotlin
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Dependency Inversion states that high-level modules shouldn’t depend on low-level modules but on abstractions. In this demo, you’ll adhere to this principle to reduce coupling in your e-commerce app.
Processing order...
Persist order amounting to 2400.0 to an SQLite Database.
interface OrderRepository {
fun saveOrder(shoppingCart: ShoppingCart): Boolean
}
class SqliteOrderRepository : OrderRepository {
override fun saveOrder(shoppingCart: ShoppingCart): Boolean {
println("Persist order amounting to ${shoppingCart.getTotalOrderPrice()} to an SQLite Database.")
return true
}
}
class OrderService(private val orderRepository: OrderRepository) {
fun processOrder(shoppingCart: ShoppingCart) {
println("Processing order...")
orderRepository.saveOrder(shoppingCart)
}
}
val orderProcessor = OrderService(SqliteOrderRepository())
Processing order...
Persist order amounting to 2400.0 to an SQLite Database.
class InMemoryOrderRepository : OrderRepository {
override fun saveOrder(shoppingCart: ShoppingCart): Boolean {
println("Persist order amounting to ${shoppingCart.getTotalOrderPrice()} to an In-Memory Database.")
return true // success
}
}
val orderProcessor = OrderService(InMemoryOrderRepository())
orderProcessor.processOrder(shoppingCart)
Processing order...
Persist order amounting to 2400.0 to an In-Memory Database.