Swift 2.0:Xcode 7中的HTTP GET错误处理

Question

我是xcode编程的新手,我正在尝试在Swift 2中实现一个发出HTTP Get请求的App.升级xcode 7后显示错误:

Cannot convert value of type 
'(NSData!, response: NSURLResponse!, err: NSError!) -> ()'
to expected argument type 
'(NSData?, NSURLResponse?, NSError?) -> Void'

(此代码段使用swift 1.2的旧错误处理.)任何人都可以帮助我,请问如何在Swift 2.0中实现它.

    request.HTTPMethod = "GET"
    let session = NSURLSession.sharedSession()
    let task = session.dataTaskWithRequest(request, completionHandler:loadedData)

    task.resume()


}

func loadedData(data:NSData!, response:NSURLResponse!, err:NSError!){

    if(err != nil)
    {
        print(err?.description)
    }
    else
    {
        var jsonResult: NSDictionary = NSDictionary()
        let httpResponse = response as! NSHTTPURLResponse
        print("\(httpResponse.statusCode)")

        if (httpResponse.statusCode == 200)
        {

            jsonResult = (try! NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers)) as! NSDictionary
            print(jsonResult)


            self.performSegueWithIdentifier("SuccessSignin", sender: self)

        }
        else if (httpResponse.statusCode == 422){

            print("422 Error Occured...")
        }


    }

}

Answer 1

方法签名已更改(参数现在是选项).此外,你必须使用try封闭在一个do catch块.并避免使用强制尝试(使用!)但更喜欢捕获可能的错误,并使用if let安全解包选项.例:

let task = session.dataTaskWithRequest(request) { (data, response, error) -> Void in
    if error != nil {
        print(error!.description)
    } else {
        if let httpResponse = response as? NSHTTPURLResponse {
            if httpResponse.statusCode == 200 {
                do {
                    if let data = data, let jsonResult = try NSJSONSerialization.JSONObjectWithData(data, options: []) as? NSDictionary {
                        print(jsonResult)
                        self.performSegueWithIdentifier("SuccessSignin", sender: self)
                    }
                } catch let JSONError as NSError {
                    print(JSONError)
                }
            } else if (httpResponse.statusCode == 422) {
                print("422 Error Occured...")
            }
        } else {
            print("Can't cast response to NSHTTPURLResponse")
        }
    }
}

task.resume()