ios - 在SWIFT中解析JSON API到WIFI和4G的不同结果

Question

我有一个提供此 JSON 的 Wordpress JSON API(它是帖子的评论列表):

JSON数据没问题，我真的有3条评论这个帖子。在我检查的 wordpress 管理员中，所有这些评论都已批准。

我试图读取这个 JSON，创建一个 NSObject Comment() 列表，并在表格 View 中显示它们。

我测试了下面的代码:

let commentURL:NSURL = NSURL(string: "http://mywebsite.com/wp_api/v1/posts/1855/comments")!

if let data:NSData = NSData(contentsOfURL: commentURL) {

    do {
        let json = try NSJSONSerialization.JSONObjectWithData(data, options: []) as! [String: AnyObject]

        if let allComments = json["comments"] as? NSArray{

            print(allComments)
        }

    } catch let error as NSError {
        print("Failed to load: \(error.localizedDescription)")
    }
}

结果很奇怪:

• 在模拟器中打开 WIFI -> allComments 数据正常
• 有带 WIFI 的 Playground -> allComments 数据正常
• 在开启 WIFI 的 iPhone/iPad iOS 9.2 设备上 -> allComments 数据正常
• 在 WIFI 关闭的 iPhone/iPad iOS 9.2 设备上，4G -> API 仅发送了 2 条评论(“测试评论编号 2”和“测试评论编号 3”)。我上面的代码没有检索到最后一条评论“Toyota”

我已经用不同的设备和网络重复了测试过程。 3G/4G 网络经常错过最后的评论。但与 WiFi 完美配合。

为什么？

编辑

我改进了我的代码，但它仍然不起作用。

func downloadCommentsFrom(post:Post, completion: ((comments: [Comment]?) -> Void)) {

    guard
        let url = NSURL(string: "http://mywebsite.com/wp_api/v1/posts/\(post.postId)/comments")
        else {return}

    let task = NSURLSession.sharedSession().dataTaskWithURL(url) {(data, response, error) in
        completion(comments: self.getCommentsFromJSONAPI(data:data!))
    }
    task.resume()
}

func getCommentsFromJSONAPI(data data:NSData) -> [Comment] {

    var comments:[Comment]=[]

    do {
        let json = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary
        if let allComments = json["comments"] as? NSArray{
             comments = allComments
             print(allComments)
        }
    } catch let error as NSError {
        print("Failed to load JSON COMMENTS: \(error.localizedDescription)")
    }

    return comments
}

编辑 2

WIFI 中的 HTTP 响应:

Optional(<NSHTTPURLResponse: 0x17db0a80> { URL: http://mywebsite.com/wp_api/v1/posts/1136/comments } { status code: 200, headers {
    "Cache-Control" = "max-age=3600, public";
    Connection = "Keep-Alive";
    "Content-Encoding" = gzip;
    "Content-Type" = "text/html";
    Date = "Sun, 20 Dec 2015 09:42:39 GMT";
    Etag = 4652938bddc2501278c4e584c4612de4;
    Expires = "Sun, 20 Dec 2015 10:42:39 GMT";
    "Keep-Alive" = "timeout=5, max=99";
    "Last-Modified" = "Thu, 01 Jan 1970 00:00:00 GMT";
    Pragma = public;
    Server = Apache;
    "Set-Cookie" = "300gp=R3395909593; path=/; expires=Sun, 20-Dec-2015 10:48:14 GMT";
    "Transfer-Encoding" = Identity;
    Vary = "Accept-Encoding,User-Agent";
    "X-Powered-By" = "PHP/5.4.45";
} })

4G 中的 HTTP 响应:

Optional(<NSHTTPURLResponse: 0x16d0d4b0> { URL: http://cestunmac.com/wp_api/v1/posts/1136/comments } { status code: 200, headers {
    Age = 208;
    "Cache-Control" = "public, max-age=3600";
    "Content-Encoding" = gzip;
    "Content-Type" = "text/html";
    Date = "Sun, 20 Dec 2015 09:40:00 GMT";
    Etag = 4652938bddc2501278c4e584c4612de4;
    Expires = "Sun, 20 Dec 2015 10:40:00 GMT";
    "Last-Modified" = "Thu, 01 Jan 1970 00:00:00 GMT";
    Pragma = public;
    Server = Apache;
    "Transfer-Encoding" = Identity;
    Vary = "Accept-Encoding,User-Agent";
    "X-Powered-By" = "PHP/5.4.45";
} })

编辑 3

这似乎是因为缓存而不是 4G 问题。我在 Playground(使用 WIFI 网络)中测试了我的代码，最后的注释也丢失了。 我尝试添加:

let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
configuration.requestCachePolicy = .ReloadIgnoringLocalAndRemoteCacheData
let urlSession:NSURLSession = NSURLSession(configuration: configuration)

或:

let configuration = NSURLSessionConfiguration.ephemeralSessionConfiguration()()
let urlSession:NSURLSession = NSURLSession(configuration: configuration)

同样的结果，在我的网络浏览器中 JSON 是正确的，但在应用程序中不是。数据尚未更新。

Answer 1

    let session = NSURLSession.sharedSession().dataTaskWithURL(commentURL!) { data, response, error in
        do {
            let json = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary

            if let allComments = json["comments"] as? [NSDictionary] {
                print(allComments)
            }

        } catch let error as NSError {
            print("Failed to load: \(error.localizedDescription)")
        }    
    }
    session.resume()