Get HTTP header fields only on iPhone
I want to get only the headers of an URL request. I have been using stringWithContentsOfURL() for all downloading so far, but now I am only interested in the headers and downloading the entire file is not feasible as it is too large.
开发者_StackOverflow中文版I have found solutions which show how to read the headers after the response has been receieved, but how do I specify in the request that I only wish to download headers. Skip the body!
Thanks.
Asynchronously send a HEAD request to the URL in question and then just access the allHeaderFields
property on HTTPURLResponse
/ NSHTTPURLResponse
.
Swift 4
var request = URLRequest(url: URL(string: "https://google.com/")!)
request.httpMethod = "HEAD"
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let response = response as? HTTPURLResponse,
let headers = response.allHeaderFields as? [String: String] else {
return
}
}
task.resume()
Objective-C
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://google.com"]];
[request setHTTPMethod:@"HEAD"];
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
NSDictionary *headers = [(NSHTTPURLResponse *)response allHeaderFields];
}];
What I've used. The code below is synchronous but you can make it asynchronous using a delegate.
NSMutableURLRequest *newRequest = ... //init your request...
NSURLResponse *response=nil;
NSError *error=nil;
[newRequest setValue:@"HEAD" forKey:@"HTTPMethod"];
[NSURLConnection sendSynchronousRequest:newRequest returningResponse:&response error:&error];
[newRequest release];
//Get MIME type from the response
NSString* MIMEType = [response MIMEType];
Edited to add replace NSURLRequest with NSMutableRequest.
only implement didReceiveResponse delegate method
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
NSInteger statusCode = [(NSHTTPURLResponse*)response statusCode];
}
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