Swift 3,没有调用URLSession dataTask completionHandler

Question

我正在写一个库,所以不使用UIKit,即使在我的iOS应用程序中,相同的代码也可以工作,但是当我在命令行中执行时却没有.在PlayGround中也似乎有效.

由于某种原因,回调没有被触发,因此print语句没有执行.

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,相同的代码也可以工作,但是当我在命令行中执行时却没有.在PlayGround中也似乎有效.

Answer 1

我从头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你的代码.(加上url创建..)我在调试器中看到了所有内容:

这一个是打印的

这一个是打印的,太

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()
    }

}

Answer 2

所做的更改是否在这里建议，现在可以使用。

通过Swift命令行程序使用NSURLSession

var sema = DispatchSemaphore( value: 0 )

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

    let session = URLSession(configuration: URLSessionConfiguration.default, delegate: self, delegateQueue: nil )

    session.dataTask(with: request) {(data, response, error) -> Void in
        if let data = data {
            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?)
            }
        }
    }.resume()
    sema.wait()
}

Answer 3

我知道答案晚了，但是如果您还没有弄清问题或在其他地方遇到问题，请尝试一下。

您需要将会话变量保存在方法范围之外（使其成为实例变量）。由于您是在函数作用域中本地定义的。在调用完成处理程序之前，将其释放，记住完成处理程序无法保留您的会话对象，并且在执行运行循环之后，垃圾收集器将取消分配您的会话对象。每当我们要从委托或完成处理程序中回调时，都需要保留此类对象。

self.session = URLSession(configuration: URLSessionConfiguration.default)