迅速在3 Playground中进行回调 [英] Callback in swift 3 Playground

问题描述

我正在尝试在操场上执行这一行代码，但得到响应的任何输出.我的代码如下:

Hi i am trying to execute this line of code in playground but getting any output of response.My Code is as follow:

func testCallbackEmpty( callback: @escaping  () -> Void) {

        DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
            callback()
        }
    }

    testCallbackEmpty(callback: { () -> Void in
        print("Hey called here")
    })


enum Result {
    case OK, FAILED
}


func mainCallback(callback: @escaping (Result) -> Void) {
    DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
        callback(Result.OK)
    }

}

mainCallback(callback: { result in
    print("Hurray \(result)")
})

推荐答案

我必须写

import UIKit

import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

位于文件顶部

这解决了.

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