在swift 3游乐场回调

Question

嗨,我想在操场上执行这行代码,但得到任何响应输出.我的代码如下:

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)")
})

Answer 1

我不得不写

import UIKit

import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

在文件的顶部

这解决了.