SWIFT: NSURLSession converts data to String

Question

In my iPhone application (being developed in SWIFT), I need to communicate with the https service (with parameters) and analyze the response.

Everything works fine, but in some cases notices that it does NOT get the expected result ... Further analysis, I found a problem with converting server data to string (NSData → NSString) ...

1). When I use UTF8 Encoding, I get null as a converted String (responseString)

    let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)

2). But with ASCII, the encoding is fine (gets the correct response server)

    let responseString = NSString(data: data, encoding: NSASCIIStringEncoding)

Below is a complete example of the code I'm trying ...

    let myUrl = NSURL(string: "https://myurl.com/myservice.asp")
    let request = NSMutableURLRequest(URL: myUrl!)

    request.HTTPMethod = "POST"
    request.timeoutInterval = 55.0
    let postString = "paramone=\(para1)&paramtwo=\(para2)&paramthree=\(para3)"

    // NOTE: Works ok with ASCII AND UTF8 both encoding types at this point...
    // request.HTTPBody = postString.dataUsingEncoding(NSASCIIStringEncoding)
    request.HTTPBody = postString.dataUsingEncoding(NSUTF8StringEncoding)

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

        if (error != nil)
        {
            println("Error: \(error)")
            println("Description: \(error.description)")
            println("Domain     : \(error.domain)")
            println("Error code : \(error.code)")
        }
        else
        {
            //???? => ENCODING PROBLEM
            // let responseString = NSString(data: data, encoding: NSASCIIStringEncoding)
            let responseString = NSString(data: data, encoding: NSUTF8StringEncoding)

            println("Response: \(responseString)")
        }
    }
    task.resume()

POSTS, ... , ASCII, UTF8...

, "" ASCII ( "" ASCII), UTF8.

, - ... .

Answer 1

NSASCIIStringEncoding 7- ASCII 0.. 127. , NSData (NS)String, 0.. 255 Unicode U + 0000.. U + 00FF. NSASCIIStringEncoding NSISOLatin1StringEncoding:

let bytes = (0 ..< 256).map { UInt8($0) }
let data = NSData(bytes: bytes, length: bytes.count)

let s1 = String(data: data, encoding: NSASCIIStringEncoding)!
let s2 = String(data: data, encoding: NSISOLatin1StringEncoding)!
print(s1 == s2) // true

, , "", , ASCII.

, ( ) , . (NS)String NSData:

let d1 = s1.dataUsingEncoding(NSASCIIStringEncoding) // nil

HTTP Content-Type = charset=..., , . fooobar.com/questions/664096/....

HTTP , .

• NSUTF8StringEncoding UTF-8 ,
• NSWindowsCP1252StringEncoding Windows-1252 encoding,
• NSISOLatin1StringEncoding ISO-8859-1.

NSString, , , , . TXT .

Answer 2

@JibW ... .

    let URL = NSURL(string: "Paste your url here")!
    var request = NSMutableURLRequest(URL: URL)
    var session = NSURLSession.sharedSession()
    request.HTTPMethod = "POST"
    request.timeInterval = 55.0
    var error: NSError?
    request.HTTPBody = NSJSONSerialization.dataWithJSONObject(parameters, options: nil, error: &error)
    request.addValue("application/json", forHTTPHeaderField: "Content-Type")
    request.addValue("application/json", forHTTPHeaderField: "Accept")


    var data: NSData!
    var response: NSURLResponse!

    var task = session.dataTaskWithRequest(request, completionHandler: {data, response, error -> Void in

        var httpResponse = response as! NSHTTPURLResponse
        println("\(httpResponse.statusCode)")

        var strData = NSString(data: data, encoding: NSUTF8StringEncoding)
        println("Body: \(strData)")

         var err: NSError?
        var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves, error: &err) as? NSDictionary

         if(err != nil) {
            println(err!.localizedDescription)
            let jsonStr = NSString(data: data, encoding: NSUTF8StringEncoding)
            println("Error could not parse JSON: '\(jsonStr)'")
        }

        else

        {
            // The JSONObjectWithData constructor didn't return an error. But, we should still
            // check and make sure that json has a value using optional binding.
            if let parseJSON = json {
                // Okay, the parsedJSON is here, let get the value for 'success' out of it
                var success = parseJSON["success"] as? Int
                println("Succes: \(success)")
            }

            else {

                // Woa, okay the json object was nil, something went worng. Maybe the server isn't running?
                let jsonStr = NSString(data: data, encoding: NSUTF8StringEncoding)
                println("Error could not parse JSON: \(jsonStr)")
            }
        }
    })

    task.resume()