OperationQueue

작업 큐라는 방식이고 병렬프로그래밍을 하기위한 개념이다.

큐에 작업들을 넣으면 알아서 별도의 Thread에서 실행시켜 준다.

let queue = OperationQueue()
queue.addOperation {
    (0...3).forEach({ print("queue1: \($0)") })
}
let operation = Operation()
operation.completionBlock = { () in
    (0...3).forEach({ print("queue2: \($0)") })
}
queue.addOperation(operation)

queue1: 0
queue2: 0
queue2: 1
queue1: 1
queue2: 2
queue1: 2
queue2: 3
queue1: 3

간단하게는 OperationQueue를 만들고 큐에 Operation을 넣으면 자동으로 Operation이 실행된다.

 

Operation을 상속받은 BlockOperation클래스도 있다.

let queue = OperationQueue()
let blockOperation = BlockOperation {
    (0...3).forEach({ print("block1: \($0)") })
}
blockOperation.addExecutionBlock {
    (0...3).forEach({ print("block2: \($0)") })
}
queue.addOperation(blockOperation)

block2: 0
block1: 0
block1: 1
block2: 1
block1: 2
block2: 2
block1: 3
block2: 3

하나 이상의 블록을 동시에 실행할 수 있다.

 

let queue = OperationQueue()
let blockOperation = BlockOperation()
blockOperation.addExecutionBlock {
    sleep(2)
    (0...3).forEach({ print("block1: \($0)") })
}
blockOperation.addExecutionBlock {
    (0...3).forEach({ print("block2: \($0)") })
}
queue.addOperation(blockOperation)
print("isFinished: \(blockOperation.isFinished)")
sleep(1)
print("isFinished: \(blockOperation.isFinished)")
sleep(3)
print("isFinished: \(blockOperation.isFinished)")

isFinished: false
block2: 0
block2: 1
block2: 2
block2: 3
isFinished: false
block1: 0
block1: 1
block1: 2
block1: 3
isFinished: true

 

BlockOperation의 모든 블럭들이 끝나야 BlockOperation이 완료된다.

let operationQueue = OperationQueue()
let blockOperation = BlockOperation {
    (0...3).forEach({ print("block1: \($0)") })
}
let blockOperation2 = BlockOperation {
    (0...3).forEach({ print("block2: \($0)") })
}
blockOperation.addDependency(blockOperation2)
operationQueue.addOperation(blockOperation)
operationQueue.addOperation(blockOperation2)

block2: 0
block2: 1
block2: 2
block2: 3
block1: 0
block1: 1
block1: 2
block1: 3

Operation에 Dependency(종속성)를 줄수 있다.

 

Queue에 넣지 않고 Operation만 사용할 수 있다.

let operation = Operation()
operation.completionBlock = {
    print("operation")
}

operation

 

let operation = Operation()
operation.completionBlock = {
    print("operation")
}
print("isCancelled: \(operation.isCancelled)")
operation.cancel()
print("isCancelled: \(operation.isCancelled)")
if !operation.isCancelled {
    operation.start()
}

isCancelled: false
isCancelled: true

cancel메서드를 호출하면 isCancelled프로퍼티의 값이 변한다.

 

NSOperation클래스는 다음 Key-Path에 대해 Key-Value Observing(KVO)(2021/01/31 - [iOS] - KVC KVO (Key-Value Coding, Key-Value Observing)) 를 준수한다.

• isCancelled
• isAsynchronous
• isExecuting
• isFinished
• isReady
• dependencies
• queuePriority
• completionBlock

 

더 많은 프로퍼티와 메서드는 공식 홈페이지에서 확인 할 수 있다.

Operation: https://developer.apple.com/documentation/foundation/operation

OperationQueue: https://developer.apple.com/documentation/foundation/operationQueue