Why my return is nil but if i press the url in chrome/safari, i can get data? - swift

Question

#IBAction func mainButtonnBeTapped(sender: AnyObject) {
let session = NSURLSession.sharedSession()
let request = NSURLRequest(URL: NSURL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTaskWithRequest(request, completionHandler: {
(data, response, error) -> Void in
let myString = NSString(data: data, encoding: NSUTF8StringEncoding)
println("this is my string: \(myString)")
})
task.resume()
}
I am using above url to try to get some data, but the return is nil, but i enter the url in chrome/safari, i can get some data.
I really don't why, can anyone help to explain?

Answer 1

This HTTP server sends a
Content-Type = application/x-javascript; charset=GBK
header field in the response, therefore you get the correct encoding from the textEncodingName property of the NSURLResponse. This can be
converted to a NSStringEncoding.
This is just a translation of the solution presented in https://stackoverflow.com/a/19885463/1187415 to Swift, plus some
simple error checking:
let session = NSURLSession.sharedSession()
let request = NSURLRequest(URL: NSURL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTaskWithRequest(request, completionHandler: {
(data, response, error) -> Void in
var usedEncoding = NSUTF8StringEncoding // Some fallback value
if let encodingName = response.textEncodingName {
let encoding = CFStringConvertEncodingToNSStringEncoding(CFStringConvertIANACharSetNameToEncoding(encodingName))
if encoding != UInt(kCFStringEncodingInvalidId) {
usedEncoding = encoding
}
}
if let myString = NSString(data: data, encoding: usedEncoding) {
println("this is my string: \(myString)")
} else {
println("failed to decode data")
}
})
task.resume()
Output:
this is my string: var hq_str_sz000609="绵世股份, ....
Minor changes are necessary for Swift 2:
let session = NSURLSession.sharedSession()
let request = NSURLRequest(URL: NSURL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTaskWithRequest(request, completionHandler: {
(data, response, error) -> Void in
var usedEncoding = NSUTF8StringEncoding // Some fallback value
if let encodingName = response?.textEncodingName {
let encoding = CFStringConvertEncodingToNSStringEncoding(CFStringConvertIANACharSetNameToEncoding(encodingName))
if encoding != UInt(kCFStringEncodingInvalidId) {
usedEncoding = encoding
}
}
if let myString = String(data: data!, encoding: usedEncoding) {
print("this is my string: \(myString)")
} else {
print("failed to decode data")
}
})
task.resume()
Update for Swift 3:
let session = URLSession.shared
let request = URLRequest(url: URL(string: "http://hq.sinajs.cn/list=sz000609")!)
let task = session.dataTask(with: request, completionHandler: {
(data, response, error) -> Void in
guard let data = data else { return }
var usedEncoding = String.Encoding.utf8 // Some fallback value
if let encodingName = response?.textEncodingName {
let encoding = CFStringConvertEncodingToNSStringEncoding(CFStringConvertIANACharSetNameToEncoding(encodingName as CFString))
if encoding != UInt(kCFStringEncodingInvalidId) {
usedEncoding = String.Encoding(rawValue: encoding)
}
}
if let myString = String(data: data, encoding: usedEncoding) {
print("this is my string: \(myString)")
} else {
print("failed to decode data")
}
})
task.resume()

Answer 2

The text you try to get is probably not UTF-8, try with another encoding, like this for example:
let myString = NSString(data: data, encoding: NSASCIIStringEncoding)
Update: read Martin R's answer for how to find the right encoding.