Downloading data use ASIHTTP

Downloading the response directly to a file

If the resource you are requesting is fairly large, you can save memory by downloading directly to a file. This way, ASIHTTPRequest won’t have to keep the whole response in memory at once.

• If the data is gzip compressed (see information on gzip compression), the compressed file will be uncompressed into downloadDestinationPath, and the temporary file will be deleted
• If the data is not compressed, the temporary file is moved to downloadDestinationPath, overwriting any previous file

Note that if the response body is empty, no file will be created. If there is a possibility that a request may return an empty body, make sure you check the file exists before you attempt to do anything with it.

Handling the response data as it arrives

If you need to process the response as it comes in (for example, you want to use a streaming parser to parse the response while it is still being downloaded), have your delegate implement request:didReceiveData: (seeASIHTTPRequestDelegate.h). Note that when you do this, ASIHTTPRequest will not populate responseData or write the response to downloadDestinationPath - you must store the response yourself if you need to.

Reading the HTTP status code

ASIHTTPRequest doesn’t do anything special with most HTTP status codes (except redirection and authentication status codes, see below for more info), so it’s up to you to look out for problems (eg: 404) and make sure you act appropriately.

ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url]; [request startSynchronous]; int statusCode = [request responseStatusCode]; NSString *statusMessage = [request responseStatusMessage];

Reading response headers

ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url]; [request startSynchronous]; NSString *poweredBy = [[request responseHeaders] objectForKey:@"X-Powered-By"]; NSString *contentType = [[request responseHeaders] objectForKey:@"Content-Type"];

Handling text encodings

ASIHTTPRequest will attempt to read the text encoding of the received data from the Content-Type header. If it finds a text encoding, it will set responseEncoding to the appropriate NSStringEncoding. If it does not find a text encoding in the header, it will use the value of defaultResponseEncoding (this defaults to NSISOLatin1StringEncoding).

When you call [request responseString], ASIHTTPRequest will attempt to create a string from the data it received, using responseEncoding as the source encoding.

Handling redirection

ASIHTTPRequest will automatically redirect to a new URL when it encounters one of the following HTTP status codes, assuming a Location header was sent:

• 301 Moved Permanently
• 302 Found
• 303 See Other

When redirection occurs, the value of the response data (responseHeaders / responseCookies / responseData / responseString etc) will reflect the content received from the final location.

Cookies set on any of the urls encountered during a redirection cycle will be stored in the global cookie store, and will be represented to the server on the redirected request when appropriate.

You can turn off automatic redirection by setting the request’s shouldRedirect property to NO.

By default, automatic redirects always redirect using a GET request (with no body). This behaviour matches the way most browsers work, not the HTTP spec, which specifies that 301 and 302 redirects should use the original method.

To preserve the original method (including the request body) for 301 and 302 redirects, setshouldUseRFC2616RedirectBehaviour to YES on the request before you start it.

原文地址：http://allseeing-i.com/ASIHTTPRequest/How-to-use