iphone - 在 iPhone 上处理电子标签

Question

知道如何在客户端处理电子标签吗？我们计划在我们的应用程序中使用来自服务器的带有图像的 eTag。

什么是 eTag，请参阅： http ://en.wikipedia.org/wiki/HTTP_ETag

Answer 1

Starting points for your study ...

NSMutableURLRequest

Here you can set eTag value for you request.

[self addValue:eTag forHTTPHeaderField:@"If-None-Match"];

This request is usable with NSURLConnection.

NSURLConnectionDelegate

Delegate of your NSURLConnection has method ...

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

... where response in your case is NSHTTPURLResponse.

You should check response statusCode in another delegate's method ...

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

... status code 304 is received when remote object is not modified. If remote object is modified and eTag is supported, you can find it in [response allHeaderFields].