Add HTTP Header to NSURLRequest

I don't think you can modify the HTTP Headers of a NSURLRequest. I think you're trying to modify a NSURLRequest object that you didn't initialize?

You could create a mutableCopy of your request and then set the header fields with the following method:

 -(void)setValue:(NSString *)value forHTTPHeaderField:(NSString *)field.

After that you can copy the mutable request back onto your NSURLRequest variable.

EDIT: Added example below

/* Create request variable containing our immutable request
 * This could also be a paramter of your method */
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.stackoverflow.com"]];

// Create a mutable copy of the immutable request and add more headers
NSMutableURLRequest *mutableRequest = [request mutableCopy];
[mutableRequest addValue:@"Hless" forHTTPHeaderField:@"X-user-nick"];

// Now set our request variable with an (immutable) copy of the altered request
request = [mutableRequest copy];

// Log the output to make sure our new headers are there    
NSLog(@"%@", request.allHTTPHeaderFields);

Already answered (and thanks to those answers), but here's a more simple example:

NSMutableURLRequest* request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:url]];
[request setValue:@"es" forHTTPHeaderField:@"Accept-Language"];

NSString *urlString = @"http://10.28.79.63:3000/testing";

NSMutableURLRequest *imageRequest = [[NSMutableURLRequest alloc] init] ;
[imageRequest setURL:[NSURL URLWithString:urlString]];
[imageRequest setHTTPMethod:@"POST"];

NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"];
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];

[imageRequest setValue:contentType forHTTPHeaderField: @"content-Type"]; 
NSMutableData *body = [NSMutableData dataWithCapacity:[imageData length] + 512];
[body appendData:[[NSString stringWithFormat:@"--%@\r\n",boundary]dataUsingEncoding:NSUTF8StringEncoding]]; 

//Here u adds the Headers which will be posted in body 

[body appendData:[[NSString stringWithString:@"Content-Disposition: form-data; content-type: application/octet-stream; name=\"userfile\"; filename=\"inLove.mp4\"\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];


[body appendData:[NSData dataWithData:imageData]];
[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];

[imageRequest setHTTPBody:body];
NSURLConnection * theConnection = [[NSURLConnection alloc] initWithRequest:imageRequest 
                                                delegate:self];