ios - 我在哪里为 Swift 2 中的 NSURLSession 指定 ReloadIgnoringLocalCacheData

Question

我有一个应用程序，使用 NSURLSession 和 p2-oauth2 每 5 秒进行一次 API 调用。我遇到了一个问题，它返回缓存的数据而不是来自 API 的更新信息。我读过this post作者:Matt Thompson，他描述了不同的缓存策略，我认为我需要使用的是 ReloadIgnoringLocalCacheData。我认为它应该放在 AppDelegate DidFinishLaunchingWithOptions 函数中。但是，我遇到的问题是我不知道在哪里或如何指定它。我还没有找到任何 Swift 解决方案。谁能告诉我我的函数应该说什么？

如果有帮助，这是我的 API 请求:

    let urlPath = "https://sandbox-api.uber.com/v1/requests/\(uberRequestId)"
    let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate

    guard let endpoint = NSURL(string: urlPath) else { print("Error creating endpoint");return }
    let request = appDelegate.oauth.request(forURL: NSURL(string:urlPath)!)
    request.setValue("application/json; charset=utf-8", forHTTPHeaderField: "Content-Type")
    request.HTTPMethod = "GET"

    //get response from Uber and iterate through to find Uber Product ID.
    NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in
        do {
            guard let dat = data else { throw JSONError.NoData }

            let result = try NSJSONSerialization.JSONObjectWithData(dat, options: NSJSONReadingOptions.MutableContainers)

            print(result)

            //set status
            status = result["status"] as! String

            print("found status...returning it back -> \(status)")
            completion(status: "\(status)")

        } catch let error as JSONError {
            print(error.rawValue)
            print("ERROR NEEDS TO BE HANDLED.")
        } catch {
            print(error)
            print("ERROR NEEDS TO BE HANDLED.")
        }
    }.resume()

Answer 1

这是正确设置缓存策略的最终请求。我添加了一行 ReloadIgnoringLocalCacheData。

let urlPath = "https://sandbox-api.uber.com/v1/requests/\(uberRequestId)"
let url:NSURL = NSURL(string: urlPath)!
let session = NSURLSession.sharedSession()
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let request = appDelegate.oauth.request(forURL: NSURL(string:urlPath)!)
request.HTTPMethod = "GET"

//added this line to set cache policy
request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringLocalCacheData
request.setValue("application/json; charset=utf-8", forHTTPHeaderField: "Content-Type")

let task = session.dataTaskWithRequest(request) {
    (
    let data, let response, let error) in

    guard let _:NSData = data, let _:NSURLResponse = response  where error == nil else {
        print("error")
        return
    }

    let dataString = NSString(data: data!, encoding: NSUTF8StringEncoding)
    print(dataString)

}

task.resume()