为什么我的return是nil，但是如果我在chrome/safari中按url，我可以得到数据？

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()
    }

我正在使用上面的url来尝试获取一些数据，但是return是零，但是我在chrome/safari中输入url，我可以得到一些数据。真不懂为什么，谁能帮忙解释一下？

Answer 1

您尝试获取的文本可能不是 UTF-8，请尝试使用其他编码，例如：

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

更新：阅读关于如何找到正确编码的回答。

Answer 2

此 HTTP 服务器发送

Content-Type = application/x-javascript; charset=GBK

header 字段，因此您可以从 NSURLResponse 的 textEncodingName 属性获得正确的编码。这可以是转换为 NSStringEncoding.

这只是 https://whosebug.com/a/19885463/1187415 到 Swift 中提出的解决方案的翻译，加上一些简单的错误检查：

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()

输出：

this is my string: var hq_str_sz000609="绵世股份, ....

Swift 2:

需要稍作改动

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()

Swift3 的更新：

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()

为什么我的return是nil，但是如果我在chrome/safari中按url，我可以得到数据？

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

nsurlrequest

swift