通过请求文件/网页的标题驻留在URL获取MIMETYPE

我需要知道文件或网页的MIMEType ，在特定的URL可用，并且根据MIMEType我将决定是否将该页面/文件加载到UIWebView 。 我知道，我可以使用NSURLResponse对象获得MIMEType ，但问题是，当我得到这个响应时，该页面已经下载了。

那么，有没有办法只在特定的URL上询问文件/网页的标题，以便我可以检查MIMEType并请求该页面/文件，只有在需要时？

Answer 1

在您确定响应的Content-Type之前，我发现您不希望在UIWebView中加载页面。 为此，您可以实现自定义NSURLProtocol。 这就是我所做的，但欢迎您随时加强或提出不同的解决方案。 请仔细阅读内联评论。

***** CustomURLProtocol.h *****

 @interface CustomURLProtocol : NSURLProtocol @end 

***** CustomURLProtocol.m *****

 @interface CustomURLProtocol () @property(nonatomic, strong) NSURLConnection * connection; @property(nonatomic, strong) NSMutableData * reponseData; @property(nonatomic, strong) NSURLRequest * originalRequest; @end @implementation CustomURLProtocol +(BOOL)canInitWithRequest:(NSURLRequest *)request { NSString * urlScheme = [request.URL.scheme lowercaseString]; //only handling HTTP or HTTPS requests which are not being handled return (![[NSURLProtocol propertyForKey:@"isBeingHandled" inRequest:request] boolValue] && ([urlScheme isEqualToString:@"http"] || [urlScheme isEqualToString:@"https"])); } +(NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request { return request; } -(void)startLoading { NSMutableURLRequest * requestCopy = [self.request mutableCopy]; [NSURLProtocol setProperty:[NSNumber numberWithBool:YES] forKey:@"isBeingHandled" inRequest:requestCopy]; self.originalRequest = requestCopy; self.connection = [NSURLConnection connectionWithRequest:requestCopy delegate:self]; } -(void)stopLoading { [self.connection cancel]; } #pragma mark - NSURLConnectionDelegate methods -(NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)response { [self.client URLProtocol:self wasRedirectedToRequest:request redirectResponse:response]; return request; } - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { if ([response isKindOfClass:[NSHTTPURLResponse class]]) { NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse *)response; NSString * contentType = [httpResponse.allHeaderFields valueForKey:@"Content-Type"]; /* Check any header here and make the descision. */ if([contentType containsString:@"application/pdf"]) { /* Let's say you don't want to load the PDF in current UIWebView instead you want to open another view controller having a webview for that. For doing that we will not inform the client about the response we received from NSURLConnection that we created. */ [self.connection cancel]; //post a notification carrying the PDF request and load this request anywhere else. [[NSNotificationCenter defaultCenter] postNotificationName:@"PDFRequest" object:self.originalRequest]; } else { /* For any other request having Content-Type other than application/pdf, we are informing the client (UIWebView or NSURLConnection) and allowing it to proceed. */ [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageAllowed]; } } } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [self.client URLProtocol:self didLoadData:data]; } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { [self.client URLProtocolDidFinishLoading:self]; } - (void)connection:(NSURLConnection *)connectionLocal didFailWithError:(NSError *)error { [self.client URLProtocol:self didFailWithError:error]; } @end 

还有一件事我忘了提到你必须在app delegate中注册CustomURLProtocol，如下所示：

 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { [NSURLProtocol registerClass:[CustomURLProtocol class]]; return YES; } 

Answer 2

您只想获取标题。 使用HTTP HEAD方法。 例：

  let request = NSMutableURLRequest(URL: NSURL(string: "your_url")!) request.HTTPMethod = "HEAD" let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in // Analyze response here } task.resume() 

Answer 3

您可以使用响应标头的“Content-Type”属性来获取内容类型：

 func getContentType(urlPath: String, completion: (type: String)->()) { if let url = NSURL(string: urlPath) { let request = NSMutableURLRequest(URL: url) request.HTTPMethod = "HEAD" let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { (_, response, error) in if let httpResponse = response as? NSHTTPURLResponse where error == nil { if let ct = httpResponse.allHeaderFields["Content-Type"] as? String { completion(type: ct) } } } task.resume() } } getContentType("http://example.com/pic.jpg") { (type) in print(type) // prints "image/jpeg" }