从'(_,_,_)类型的抛出函数向抛出函数类型'抛出函数类型'(URLResponse?,Data ?, Error?)无效转换 - >无效
问题描述:
我试图关注Ray Wenderlich网站的一个教程,用于学习使用仪器。示例代码的编写是Swift 2,我相信在我被允许运行它之前,我必须将代码迁移到最新的Swift版本。我已经通过了转换错误得到一半的方式,但我难倒下面的代码区:从'(_,_,_)类型的抛出函数向抛出函数类型'抛出函数类型'(URLResponse?,Data ?, Error?)无效转换 - >无效
class Flickr {
let processingQueue = OperationQueue()
func searchFlickrForTerm(_ searchTerm: String, completion : @escaping (_ results: FlickrSearchResults?, _ error : NSError?) -> Void){
let searchURL = flickrSearchURLForSearchTerm(searchTerm)
let searchRequest = URLRequest(url: searchURL)
NSURLConnection.sendAsynchronousRequest(searchRequest, queue: processingQueue) {response, data, error in
if error != nil {
completion(nil,error as! NSError)
return
}
var JSONError : NSError?
let resultsDictionary = try JSONSerialization.jsonObject(with: data!, options: []) as? NSDictionary
if JSONError != nil {
completion(nil, JSONError)
return
}
switch (resultsDictionary!["stat"] as! String) {
case "ok":
print("Results processed OK")
case "fail":
let APIError = NSError(domain: "FlickrSearch", code: 0, userInfo: [NSLocalizedFailureReasonErrorKey:resultsDictionary!["message"]!])
completion(results: nil, error: APIError)
return
default:
let APIError = NSError(domain: "FlickrSearch", code: 0, userInfo: [NSLocalizedFailureReasonErrorKey:"Unknown API response"])
completion(nil, APIError)
return
}
let photosContainer = resultsDictionary!["photos"] as! NSDictionary
let photosReceived = photosContainer["photo"] as! [NSDictionary]
let flickrPhotos : [FlickrPhoto] = photosReceived.map {
photoDictionary in
let photoID = photoDictionary["id"] as? String ?? ""
let title = photoDictionary["title"] as? String ?? ""
let farm = photoDictionary["farm"] as? Int ?? 0
let server = photoDictionary["server"] as? String ?? ""
let secret = photoDictionary["secret"] as? String ?? ""
let flickrPhoto = FlickrPhoto(photoID: photoID, title: title, farm: farm, server: server, secret: secret)
return flickrPhoto
}
DispatchQueue.main.async(execute: {
completion(FlickrSearchResults(searchTerm: searchTerm, searchResults: flickrPhotos), nil)
})
}
}
fileprivate func flickrSearchURLForSearchTerm(_ searchTerm:String) -> URL {
let escapedTerm = searchTerm.addingPercentEscapes(using: String.Encoding.utf8)!
let URLString = "https://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=\(apiKey)&text=\(escapedTerm)&per_page=30&format=json&nojsoncallback=1"
return URL(string: URLString)!
}
}
我得到了下面的代码行的错误:
NSURLConnection.sendAsynchronousRequest(searchRequest, queue: processingQueue) {response, data, error in
if error != nil {
completion(nil,error as! NSError)
return
}
我有一点困惑,应该如何修改这些do,try,catch,所以任何帮助都会被赞赏,所以我可以运行app来玩弄Instruments。
这里是一个教程链接:https://www.raywenderlich.com/97886/instruments-tutorial-with-swift-getting-started
答
这个替换您的Flickr类。
class Flickr {
let processingQueue = OperationQueue()
func searchFlickrForTerm(_ searchTerm: String, completion : @escaping (_ results: FlickrSearchResults?, _ error : NSError?) -> Void){
let searchURL = flickrSearchURLForSearchTerm(searchTerm)
let searchRequest = URLRequest(url: searchURL)
NSURLConnection.sendAsynchronousRequest(searchRequest, queue: processingQueue) {response, data, error in
guard let data = data, error == nil else {
completion(nil, error as NSError?)
return
}
guard let jsonObject = try? JSONSerialization.jsonObject(with: data,
options: JSONSerialization.ReadingOptions(rawValue: 0)),
let resultsDictionary = jsonObject as? Dictionary<String, Any>
else
{
return
}
switch (resultsDictionary["stat"] as! String) {
case "ok":
print("Results processed OK")
case "fail":
let APIError = NSError(domain: "FlickrSearch", code: 0, userInfo: [NSLocalizedFailureReasonErrorKey:resultsDictionary["message"]!])
completion(nil, APIError)
return
default:
let APIError = NSError(domain: "FlickrSearch", code: 0, userInfo: [NSLocalizedFailureReasonErrorKey:"Unknown API response"])
completion(nil, APIError)
return
}
let photosContainer = resultsDictionary["photos"] as! NSDictionary
let photosReceived = photosContainer["photo"] as! [NSDictionary]
let flickrPhotos : [FlickrPhoto] = photosReceived.map {
photoDictionary in
let photoID = photoDictionary["id"] as? String ?? ""
let title = photoDictionary["title"] as? String ?? ""
let farm = photoDictionary["farm"] as? Int ?? 0
let server = photoDictionary["server"] as? String ?? ""
let secret = photoDictionary["secret"] as? String ?? ""
let flickrPhoto = FlickrPhoto(photoID: photoID, title: title, farm: farm, server: server, secret: secret)
return flickrPhoto
}
DispatchQueue.main.async(execute: {
completion(FlickrSearchResults(searchTerm: searchTerm, searchResults: flickrPhotos), nil)
})
}
}
fileprivate func flickrSearchURLForSearchTerm(_ searchTerm:String) -> URL {
let escapedTerm = searchTerm.addingPercentEscapes(using: String.Encoding.utf8)!
let URLString = "https://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=\(apiKey)&text=\(escapedTerm)&per_page=30&format=json&nojsoncallback=1"
return URL(string: URLString)!
}
}
对不起,间距都搞砸了,但问题是你没有正确地进行错误处理。当你做JSONSerialization时,它可以抛出,所以你必须把它包装在do catch块中,或者你可以使用!如果抛出错误或忽略抛出和崩溃?如果失败返回nil。
问题是你有'try'可以抛出错误,但是你没有捕获它,所以它假设闭包因此需要抛出错误,而不是。只需''''''''''可以在闭包中使用'try'抛出的错误或者使用'try?',它不会抛出错误。 – Rob