ios - Swift中的完成处理程序错误

我正在尝试使用Swift中的完成处理程序来制作自己的方法:

func callURL(url: NSURL, username: String, password: String, completionHandler: (NSData?) -> ()?) {
    let request = NSMutableURLRequest(URL: url)
    let un = username
    let pass = password
    let loginString = NSString(format: "%@:%@", un, pass)
    let loginData: NSData = loginString.dataUsingEncoding(NSUTF8StringEncoding)!
    let base64LoginString = loginData.base64EncodedStringWithOptions(NSDataBase64EncodingOptions(0))
    request.setValue("Basic \(base64LoginString)", forHTTPHeaderField: "Authorization")
    completionHandler(NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) {(response, data, error) in
        return data
    })
}

但是在完成处理程序行上出现错误:

'Void' is not convertible to 'NSData'

最佳答案

您正在返回NSData的函数(NSURLConnection回调)中返回Void。

您应该像这样在NSURLConnection回调中调用completionHandler:

func callURL(url: NSURL, username: String, password: String, completionHandler: ((NSData?) -> Void)?) {
    let request = NSMutableURLRequest(URL: url)
    let un = username
    let pass = password
    let loginString = NSString(format: "%@:%@", un, pass)
    let loginData: NSData = loginString.dataUsingEncoding(NSUTF8StringEncoding)!
    let base64LoginString = loginData.base64EncodedStringWithOptions(NSDataBase64EncodingOptions(0))
    request.setValue("Basic \(base64LoginString)", forHTTPHeaderField: "Authorization")
    NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) {
        response, data, error in
        if let completion = completionHandler {
            completion(data)
        }
    }