Playground에서 비동기 콜백을 실행하는 방법

Playground에서 비동기 콜백을 실행하는 방법

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많은 Cocoa 및 CocoaTouch 메소드에는 Objective-C의 블록 및 Swift의 Closures로 완료 콜백이 구현되어 있습니다. 그러나 Playground에서 이러한 작업을 시도 할 때 완료가 호출되지 않습니다. 예를 들면 다음과 같습니다.

// Playground - noun: a place where people can play

import Cocoa
import XCPlayground

let url = NSURL(string: "http://stackoverflow.com")
let request = NSURLRequest(URL: url)

NSURLConnection.sendAsynchronousRequest(request, queue:NSOperationQueue.currentQueue() {
response, maybeData, error in

    // This block never gets called?
    if let data = maybeData {
        let contents = NSString(data:data, encoding:NSUTF8StringEncoding)
        println(contents)
    } else {
        println(error.localizedDescription)
    }
}

내 놀이터 타임 라인에서 콘솔 출력을 볼 수 있지만 println완료 블록 의 콘솔 출력은 호출되지 않습니다 ...

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런 루프를 수동으로 (또는 런 루프가 필요없는 비동기 코드의 경우 디스패치 세마포어와 같은 다른 대기 방법 사용) 수동으로 실행할 수 있지만 놀이터에서 비동기 작업을 대기하기 위해 제공하는 "내장"방법은 다음과 같습니다. XCPlayground프레임 워크를 가져 와서 설정 XCPlaygroundPage.currentPage.needsIndefiniteExecution = true합니다. 이 속성을 설정 한 경우 최상위 수준 놀이터 소스가 완료되면 놀이터를 중지하는 대신 기본 실행 루프를 계속 돌리므로 비동기 코드가 실행될 수 있습니다. 타임 아웃 후 기본적으로 놀이터는 30 초로 종료되지만, 보조 편집기를 열고 타임 라인 보조를 표시하면 구성 할 수 있습니다. 타임 아웃은 오른쪽 아래에 있습니다.

예를 들어 Swift 3에서 ( URLSession대신 사용 NSURLConnection) :

import UIKit
import PlaygroundSupport

let url = URL(string: "http://stackoverflow.com")!

URLSession.shared.dataTask(with: url) { data, response, error in
    guard let data = data, error == nil else {
        print(error ?? "Unknown error")
        return
    }

    let contents = String(data: data, encoding: .utf8)
    print(contents!)
}.resume()

PlaygroundPage.current.needsIndefiniteExecution = true

또는 스위프트 2에서 :

import UIKit
import XCPlayground

let url = NSURL(string: "http://stackoverflow.com")
let request = NSURLRequest(URL: url!)

NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.currentQueue()) { response, maybeData, error in
    if let data = maybeData {
        let contents = NSString(data:data, encoding:NSUTF8StringEncoding)
        println(contents)
    } else {
        println(error.localizedDescription)
    }
}

XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

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This API changed again in Xcode 8 and it was moved to the PlaygroundSupport:

import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

This change was mentioned in Session 213 at WWDC 2016.

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As of XCode 7.1, XCPSetExecutionShouldContinueIndefinitely() is deprecated. The correct way to do this now is to first request indefinite execution as a property of the current page:

import XCPlayground

XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

…then indicate when execution has finished with:

XCPlaygroundPage.currentPage.finishExecution()

For example:

import Foundation
import XCPlayground

XCPlaygroundPage.currentPage.needsIndefiniteExecution = true

NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: "http://stackoverflow.com")!) {
    result in
    print("Got result: \(result)")
    XCPlaygroundPage.currentPage.finishExecution()
}.resume()

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The reason the callbacks are not called is because the RunLoop isn't running in Playground (or in REPL mode for that matter).

A somewhat janky, but effective, way to make the callbacks operate is with a flag and then manually iterating on the runloop:

// Playground - noun: a place where people can play

import Cocoa
import XCPlayground

let url = NSURL(string: "http://stackoverflow.com")
let request = NSURLRequest(URL: url)

var waiting = true

NSURLConnection.sendAsynchronousRequest(request, queue:NSOperationQueue.currentQueue() {
response, maybeData, error in
    waiting = false
    if let data = maybeData {
        let contents = NSString(data:data, encoding:NSUTF8StringEncoding)
        println(contents)
    } else {
        println(error.localizedDescription)
    }
}

while(waiting) {
    NSRunLoop.currentRunLoop().runMode(NSDefaultRunLoopMode, beforeDate: NSDate())
    usleep(10)
}

This pattern has often been used in Unit Tests which need to test async callbacks, for example: Pattern for unit testing async queue that calls main queue on completion

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The new APIs as for XCode8, Swift3 and iOS 10 are,

// import the module
import PlaygroundSupport
// write this at the beginning
PlaygroundPage.current.needsIndefiniteExecution = true
// To finish execution
PlaygroundPage.current.finishExecution()

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Swift 4, Xcode 9.0

import Foundation
import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

let url = URL(string: "https://jsonplaceholder.typicode.com/posts/1")!

let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
    guard error == nil else {
        print(error?.localizedDescription ?? "")
        return
    }

    if let data = data, let contents = String(data: data, encoding: String.Encoding.utf8) {
        print(contents)
    }
}
task.resume()

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Swift 3, xcode 8, iOS 10

Notes:

Tell the compiler that the playground file requires "indefinite execution"

Manually terminate execution via a call to PlaygroundSupport.current.completeExecution() within your completion handler.

You may run into problems with the cache directory and to resolve this you will need to manually re-instantiate the UICache.shared singleton.

Example:

import UIKit
import Foundation
import PlaygroundSupport

// resolve path errors
URLCache.shared = URLCache(memoryCapacity: 0, diskCapacity: 0, diskPath: nil)

// identify that the current page requires "indefinite execution"
PlaygroundPage.current.needsIndefiniteExecution = true

// encapsulate execution completion
func completeExecution() {
    PlaygroundPage.current.finishExecution()
}

let url = URL(string: "http://i.imgur.com/aWkpX3W.png")

let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in
    var image = UIImage(data: data!)

    // complete execution
    completeExecution()
}

task.resume()

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NSURLConnection.sendAsynchronousRequest(...)    
NSRunLoop.currentRunLoop().run()

참고URL : https://stackoverflow.com/questions/24058336/how-do-i-run-asynchronous-callbacks-in-playground