Swift 3，未调用 URLSession dataTask completionHandler [英] Swift 3, URLSession dataTask completionHandler not called

问题描述

我正在编写一个库，所以不使用 UIKit，即使在我的 iOS 应用程序中，相同的代码也能工作，但是当我在命令行中执行时却没有.在 PlayGround 中，它似乎也有效.

I am writing a library, So not using UIKit, Even in my iOS app same code works, but when i execute in command line in doesn't . In PlayGround also it seems working.

由于某种原因没有触发回调，所以没有执行打印语句.

For some reason callback is not getting triggered, so print statements are not executing.

internal class func post(request: URLRequest, responseCallback: @escaping (Bool, AnyObject?) -> ()) {
    execTask(request: request, taskCallback: { (status, resp)  -> Void in
            responseCallback(status, resp)
    })
}

internal class func clientURLRequest(url: URL, path: String, method: RequestMethod.RawValue,  params: Dictionary<String, Any>? = nil) -> URLRequest {
    var request = URLRequest(url: url)
    request.httpMethod = method
    do {
        let jsonData = try JSONSerialization.data(withJSONObject: (params! as [String : Any]), options: .prettyPrinted)

        request.setValue("application/json; charset=utf-8", forHTTPHeaderField: "Content-Type")
        request.httpBody = jsonData
    } catch let error as NSError {
        print(error)
    }
    return request
}

private class func execTask(request: URLRequest, taskCallback: @escaping (Bool,
    AnyObject?) -> ()) {

    let session = URLSession(configuration: URLSessionConfiguration.default)
    print("THIS LINE IS PRINTED")
    let task = session.dataTask(with: request, completionHandler: {(data, response, error) -> Void in
        if let data = data {
            print("THIS ONE IS NOT PRINTED")
            let json = try? JSONSerialization.jsonObject(with: data, options: [])
            if let response = response as? HTTPURLResponse , 200...299 ~= response.statusCode {
                taskCallback(true, json as AnyObject?)
            } else {
                taskCallback(false, json as AnyObject?)
            }
        }
    })
    task.resume()
}

编辑 -:我正在编写一个库，所以不使用 UIKit，即使在我的 iOS 应用程序中，相同的代码也能工作，但是当我在命令行中执行时却没有.在 PlayGround 中，它似乎也有效.

Edits -: I am writing a library, So not using UIKit, Even in my iOS app same code works, but when i execute in command line in doesn't . In PlayGround also it seems working.

推荐答案

我从头开始做了一个简单的应用程序.(Xcode 8 beta 6/swift 3)在控制器中，我粘贴了您的代码.(加上网址创建..)我在调试器中看到了所有内容:

I made a simple App from scratch. (Xcode 8 beta 6 / swift 3) In controller I pasted Your code. (plus url creation..) I see all in debugger:

这个是打印出来的

这个也是印刷的

我回来了

所以它似乎工作.

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let URLString = "https://apple.com"
        let url = URL(string: URLString)
        let request = URLRequest(url: url!)


        ViewController.execTask(request: request) { (ok, obj) in

            print("I AM BACK")

        }

    }

    private class func execTask(request: URLRequest, taskCallback: @escaping (Bool,
        AnyObject?) -> ()) {

        let session = URLSession(configuration: URLSessionConfiguration.default)
        print("THIS LINE IS PRINTED")
        let task = session.dataTask(with: request, completionHandler: {(data, response, error) -> Void in
            if let data = data {
                print("THIS ONE IS PRINTED, TOO")
                let json = try? JSONSerialization.jsonObject(with: data, options: [])
                if let response = response as? HTTPURLResponse , 200...299 ~= response.statusCode {
                    taskCallback(true, json as AnyObject?)
                } else {
                    taskCallback(false, json as AnyObject?)
                }
            }
        })
        task.resume()
    }

}

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