ios - 方法总是返回 Nil

Question

我正在尝试从 Fitbit 服务器获取 JSON 数据并打印它。当我运行第一个函数时，我总是得到 nil。但是，当我运行第二个函数时，它会正确打印数据。我猜这与 iPhone 从服务器获取 JSON 所需的时间有关，但我完全不知道如何解决它。我的最终目标是返回数据，但显然我无法从完成处理程序中执行此操作。

static func getFitbitData(resource: ResourcePath, date: Date) -> Int? {
        var rawData: NSData?
        let request = oauth.request(forURL: NSURL(string: "https://api.fitbit.com/1/user/-/\(resource.rawValue)/date/\(date.toString())/1d.json")!)
        let task = oauth.session.dataTaskWithRequest(request) { data, response, error in
            if error != nil {
                print("[ERROR] An error occured during request: \(error)")
            }
            else {
                print("[SUCCESS] Data retrieved successfully")
                rawData = data!
            }
        }
        task.resume()
        return ParsingEngine.parseFitbitData(ResourcePath.calories, data: rawData!)
    }



static func getFitbitData(resource: ResourcePath, date: Date) -> Int? {
        let request = oauth.request(forURL: NSURL(string: "https://api.fitbit.com/1/user/-/\(resource.rawValue)/date/\(date.toString())/1d.json")!)
        let task = oauth.session.dataTaskWithRequest(request) { data, response, error in
            if error != nil {
                print("[ERROR] An error occured during request: \(error)")
            }
            else {
                print("[SUCCESS] Data retrieved successfully")
                print(ParsingEngine.parseFitbitData(ResourcePath.calories, data: data!))
            }
        }
        task.resume()
        return nil
    }

Answer 1

您说得对，该函数在您的数据从服务器填充之前就返回了。为什么你不能从完成处理程序中做到这一点？这应该有效:

static func getFitbitData(resource: ResourcePath, date: Date, completion: (data: Int?) -> Void) {
        var rawData: NSData?
        let request = oauth.request(forURL: NSURL(string: "https://api.fitbit.com/1/user/-/\(resource.rawValue)/date/\(date.toString())/1d.json")!)
        let task = oauth.session.dataTaskWithRequest(request) { data, response, error in
            if error != nil {
                print("[ERROR] An error occured during request: \(error)")
            }
            else {
                print("[SUCCESS] Data retrieved successfully")
                let endData = ParsingEngine.parseFitbitData(ResourcePath.calories, data: data!)
                completion(endData)
            }
        }
        task.resume()
    }

你可以这样调用它:

FitbitService.getFitbitData(myResource, date: myDate) { data in
   //work with your data here
}