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Swift：非同期urlsession関数内で値を返すにはどうすればよいですか？

ご覧のとおり、JSONファイルを受け取り、SwiftyJSONを使用して解析し、totalTimeを返そうとしていますが、許可されません。どうすればよいですか？

func googleDuration(Origin: String, destination: String) -> Int{
    // do calculations Origin and destiantion with google distance matrix api

    let originFix = Origin.stringByReplacingOccurrencesOfString(" ", withString: "+", options: NSStringCompareOptions.LiteralSearch, range: nil);
    let destinationFix = destination.stringByReplacingOccurrencesOfString(" ", withString: "+", options: NSStringCompareOptions.LiteralSearch, range: nil);

    let urlAsString = "https://maps.googleapis.com/maps/api/distancematrix/json?origins="+originFix+"&destinations="+destinationFix;
    println(urlAsString);

    let url = NSURL(string: urlAsString)!
    let urlSession = NSURLSession.sharedSession()

    let task = urlSession.dataTaskWithURL(url, completionHandler: {data, response, error -> Void in
        if error != nil {
            // If there is an error in the web request, print it to the console
            println(error.localizedDescription)
        }

        println("parsing JSON");
        let json = JSON(data: data);
        if (json["status"].stringValue == "OK") {
            if let totalTime = json["rows"][0]["elements"][0]["duration"]["value"].integerValue {
                println(totalTime);
            }
        }
    })
    task.resume();
}
jsonasynchronousswiftnsurlsession
12
teo751

独自のcompletionHandlerクロージャパラメータを追加し、タスクの完了時に呼び出す必要があります。

func googleDuration(Origin: String, destination: String, completionHandler: (Int?, NSError?) -> Void ) -> NSURLSessionTask {
    // do calculations Origin and destiantion with google distance matrix api

    let originFix = Origin.stringByReplacingOccurrencesOfString(" ", withString: "+", options: NSStringCompareOptions.LiteralSearch, range: nil);
    let destinationFix = destination.stringByReplacingOccurrencesOfString(" ", withString: "+", options: NSStringCompareOptions.LiteralSearch, range: nil);

    let urlAsString = "https://maps.googleapis.com/maps/api/distancematrix/json?origins="+originFix+"&destinations="+destinationFix
    println(urlAsString)

    let url = NSURL(string: urlAsString)!
    let urlSession = NSURLSession.sharedSession()

    let task = urlSession.dataTaskWithURL(url) { data, response, error -> Void in
        if error != nil {
            // If there is an error in the web request, print it to the console
            // println(error.localizedDescription)
            completionHandler(nil, error)
            return
        }

        //println("parsing JSON");
        let json = JSON(data: data)
        if (json["status"].stringValue == "OK") {
            if let totalTime = json["rows"][0]["elements"][0]["duration"]["value"].integerValue {
                // println(totalTime);
                completionHandler(totalTime, nil)
                return
            }
            let totalTimeError = NSError(domain: kAppDomain, code: kTotalTimeError, userInfo: nil) // populate this any way you prefer
            completionHandler(nil, totalTimeError)
        }
        let jsonError = NSError(domain: kAppDomain, code: kJsonError, userInfo: nil) // again, populate this as you prefer
        completionHandler(nil, jsonError)
    }
    task.resume()
    return task
}

また、呼び出し元がタスクをキャンセルできるようにしたい場合に備えて、これでNSURLSessionTaskを返すようにします。

とにかく、あなたはこれを次のように呼ぶでしょう：

googleDuration(Origin, destination: destination) { totalTime, error in
    if let totalTime = totalTime {
        // use totalTime here
    } else {
        // handle error     
    }
}
11
Rob

もう一つの例：

   class func getExchangeRate(#baseCurrency: String, foreignCurrency:String, completion: ((result:Double?) -> Void)!){
    let baseURL = kAPIEndPoint
    let query = String(baseCurrency)+"_"+String(foreignCurrency)

    var finalExchangeRate = 0.0
    if let url = NSURL(string: baseURL + query) {
        NSURLSession.sharedSession().dataTaskWithURL(url) { data, response, error in

            if ((data) != nil) {
                let jsonDictionary:NSDictionary = NSJSONSerialization.JSONObjectWithData(data!, options: nil, error: nil) as NSDictionary

                if let results = jsonDictionary["results"] as? NSDictionary{
                    if let queryResults = results[query] as? NSDictionary{
                        if let exchangeRate = queryResults["val"] as? Double{
                            let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT
                            dispatch_async(dispatch_get_global_queue(priority, 0)) {
                                dispatch_async(dispatch_get_main_queue()) {
                                    completion(result: exchangeRate)
                                }
                            }

                        }
                    }
                }
            }
            else {
                completion(result: nil)
            }

        }.resume()
    }
}

コール：

 Currency.getExchangeRate(baseCurrency: "USD", foreignCurrency: "EUR") { (result) -> Void in
        if let exchangeValue = result {
            print(exchangeValue)
        }
    }
2
ericgu

もう一つの例：

func getJason(url: NSURL, completionHandler: (String?, NSError?) -> Void ) -> NSURLSessionTask {

    var finalData: String!
    let task = NSURLSession.sharedSession().dataTaskWithURL(url) { (data, response, error) -> Void in

        if error != nil{

            completionHandler(nil, error)
            return
        }
        else{

        if let urlContent = data{

            do{
                let jsonData = try NSJSONSerialization.JSONObjectWithData(urlContent, options: NSJSONReadingOptions.MutableContainers)

                if let ip = jsonData["ip"]{

                    finalData = ip as? String
                    completionHandler(finalData, nil)
                    return
                }

            }catch{
                print("EMPTY")
            }

        }

    }
}
    task.resume()
    return task
}

それから私はviewDidLoadでそれを呼び出しました

getJason(url) { (ipAddress, error) -> Void in

        if error != nil{

            print(error)
        }
        else{
            if let ip = ipAddress{          //To get rid of optional

        self.ipLabelDisplay.text = "Your Ip Address is: \(ip)"

            }

        }
    }
0
Kegham K.