an error during a type conversion in Swift 3

Question

I'm studying Swift Animation. Its material is written in Swift 2, so I had to convert its original code into Swift 3. I have learned from it along, but now I have a big problem. Xcode successfully built this code but produced a runtime error message. (I attached the image file.)

I can't solve this at all on my own as I guess I have little experience. How can I fix this? Help.

func setQuote() {

    //fadeOut


    //getting data from API
    let dataService = DataService()
    dataService.getQuoteData {(quote, author) -> Void in

        UIView.animate(withDuration: 0.5, animations: {

            //fadeIn and backgroundColor


            //quote
            self.quoteLabel.text = quote


            //author - optional binding

            //if no author


            }, completion:nil)


    }
}


class DataService {

    func getQuoteData(_ completion: @escaping (_ quote: String, _ author: String?) -> ()) {

        let url = URL(string: "http://api.forismatic.com/api/1.0/?method=getQuote&lang=en&format=json")!

        URLSession.shared.dataTask(with: url, completionHandler: { ( data: Data?, response: URLResponse?, error: NSError?) -> Void in

            do {
                let jsonDictionary = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! NSDictionary

                let aQuote = jsonDictionary["quoteText"] as! String
                let aAuthor = jsonDictionary["quoteAuthor"] as! String

                DispatchQueue.main.async(execute: { () -> Void in
                    completion(aQuote, aAuthor)
                })

            } catch {
                print("invalid json query")
            }
        } as! (Data?, URLResponse?, Error?) -> Void).resume()
    }

}

Answer 1

You can try rewrite it like this

    let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
        do {
            let jsonDictionary = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.mutableContainers) as! NSDictionary

            let aQuote = jsonDictionary["quoteText"] as! String
            let aAuthor = jsonDictionary["quoteAuthor"] as! String

            DispatchQueue.main.async(execute: { () -> Void in
                completion(aQuote, aAuthor)
            })

        } catch {
            print("invalid json query")
        }
    }

    task.resume()

or simply change the ( data: Data?, response: URLResponse?, error: NSError?) -> Void to ( data, response, error) -> Void and remove the as! ... as! ...