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September 24, 2019 13:40
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독립적으로 실행가능한 계산을 모으기: Apply 타입 클래스 사용
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| case class Pack(orders: Seq[Order], orderItems: Seq[OrderItem], products: Seq[Product]) | |
| // 1. for-comprehension에서 flatMap 체이닝: 순서대로 실행된다. | |
| for { | |
| orders <- orderRepository.findAll() | |
| orderItems <- orderItemRepository.findAll() | |
| products <- productRepository.findAll() | |
| } yield Pack(orders, orderItems, products) | |
| // 2. future를 먼저 받아놓고 flatMap 체이닝: 동시에 여러 개의 Future를 진행할 수 있지만, 코드가 많아진다. | |
| val ordersFuture = orderRepository.findAll() | |
| val orderItemsFuture = orderItemRepository.findAll() | |
| val productsFuture = productRepository.findAll() | |
| for { | |
| orders <- ordersFuture | |
| orderItems <- orderItemsFuture | |
| products <- productsFuture | |
| } yield Pack(orders, orderItems, products) | |
| // 3. Apply.mapN 사용: 간단하다. | |
| import cats.instances.future._ | |
| import cats.syntax.apply._ | |
| ( | |
| orderRepository.findAll(), | |
| orderItemRepository.findAll(), | |
| productRepository.findAll() | |
| ).mapN(Pack) |
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