json - NSURLSession.dataTaskWithRequest 不工作

Question

我正在尝试制作一个通用类，该类将从 URL 读取 JSON 数据，并使用从 JSON 数据创建的 NSDictionary 执行回调。我已经创建了一个静态类来执行该功能，但它似乎在 dataTaskWithRequest 之后不起作用。

[我的代码]

import Foundation

class LoadJsonFromNetwork {
    static func LoadJsonFromNetwork(url:NSURL, completion:((NSDictionary) -> ())) {
        print("Creating request")
        let urlRequest = NSMutableURLRequest(URL: url, cachePolicy: .ReloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 15.0)
        print("Creating session")
        let session = NSURLSession.sharedSession()
        print("Send request")
        session.dataTaskWithRequest(urlRequest) {
            (data: NSData?, response: NSURLResponse?, error: NSError?) in
            print("Checking error and nil data")
            if (error == nil && data != nil) {
                print("Request json dictionary from nsdata")
                if let result = self.NSDataToJson(data!) {
                    print("Dispatching to main queue")
                    dispatch_async(dispatch_get_main_queue()) {
                        print("Calling callback")
                        completion(result)
                    }
                }
            } else {
                print(error!.description)
            }
        }
    }

    private static func NSDataToJson(data:NSData) -> NSDictionary? {
        do {
            print("Serializing JSON")
            let json: AnyObject? = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.AllowFragments)
            print("Cretaing NSDictionary")
            let result = json as? NSDictionary
            print("Returning result")
            return result
        } catch {
            return nil
        }
    }
}

[我在控制台中的结果]

Creating request
Creating session
Send request

Answer 1

您忘记了 resume() 任务。请找到您的以下编辑代码!

static func LoadJsonFromNetwork(url:NSURL, completion:((NSDictionary) -> ())) {
    print("Creating request")
    let urlRequest = NSMutableURLRequest(URL: url, cachePolicy: .ReloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 15.0)
    print("Creating session")
    let session = NSURLSession.sharedSession()
    print("Send request")
    let task = session.dataTaskWithRequest(urlRequest) {
        (data: NSData?, response: NSURLResponse?, error: NSError?) in
        print("Checking error and nil data")
        if (error == nil && data != nil) {
           print("Request json dictionary from nsdata")
           if let result = self.NSDataToJson(data!) {
               print("Dispatching to main queue")
               dispatch_async(dispatch_get_main_queue()) {
                   print("Calling callback")
                   completion(result)
               }
           }
       } else {
           print(error!.description)
       }
    }
    task.resume() //you need to call this
}