NSURLProtocol doesn't get complete NSURLRequest
Problem : I have my subclass of NSURLProtocol, but the NSURLRequest returned by +canonicalRequestForRequest: or the request returned by -connection:willSendRequest:redirectResponse: are never passed to my URL protocol instance.
Details : In my subclass of NSURLProtocol , I implement the method +canonicalRequestForRequest: to add an HTTP header to the request. The header is added successfully, but when -startLoading is called on my URL protocol, self.request doesn't include that header.
Additionally, when connection:willSendRequest:redirectResponse: is called on the delegate of the NSURLConnection , whatever request is returned by that method never reaches my URL protocol instance either.
I think the problem lies in that initWithRequest:cachedResponse:client: is called before +canonicalRequestForRequest: or connection:willSendRequest:redirectResponse: are called, and the resulting requests from those 2 methods are never passed to my URL protocol instance after it has been alloc / init .
Is this a bug in Apple's URL loading system? Is there a workaround? Am I doing something wrong?
Update on April 6, 2014
Here is some sample code. I set 2 headers: one in -[APViewController connection:willSendRequest:redirectResponse:] called X-WillSendRequestTest and the other one in +[APURLProtocol canonicalRequestForRequest:] . Neither one is in the NSURLRequest fetched by calling self.request within -[APURLProtocol startLoading] .
APViewController.m (the delegate of NSURLProtocol)
- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)redirectResponse {
NSLog(@"Will send request: %@", request);
NSMutableURLRequest *newRequest = [request mutableCopy];
// This header will not be in self.request when fetched within the -[APURLProtocol start loading] method.
[newRequest setValue:@"12345" forHTTPHeaderField:@"X-WillSendRequestTest"];
NSLog(@"New request: %@", newRequest);
return newRequest;
}
APURLProtocol.m
@interface APURLProtocol () <NSURLConnectionDelegate, NSURLConnectionDataDelegate>
// Private properties
@property (nonatomic, strong) NSURLConnection *connection;
@end
@implementation APURLProtocol
#pragma mark -
#pragma mark Init methods
- (id)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id<NSURLProtocolClient>)client {
NSLog(@"%@", NSStringFromSelector(_cmd));
if ((self = [super initWithRequest:request cachedResponse:cachedResponse client:client])) {
}
return self;
}
#pragma mark -
#pragma mark dealloc
- (void)dealloc {
NSLog(@"%@", NSStringFromSelector(_cmd));
[_connection cancel];
}
#pragma mark -
#pragma mark Inherited class methods
+ (BOOL)canInitWithRequest:(NSURLRequest *)request {
NSLog(@"%@ %@", NSStringFromSelector(_cmd), request);
id requestIsHandled = [self propertyForKey:kAPURLProtocolHandledRequest inRequest:request];
if (requestIsHandled == nil
&& ([request.URL.scheme caseInsensitiveCompare:@"http"] == NSOrderedSame
|| [request.URL.scheme caseInsensitiveCompare:@"https"] == NSOrderedSame
|| [request.URL.scheme caseInsensitiveCompare:@"ftp"] == NSOrderedSame)) {
NSLog(@"YES");
return YES;
}
NSLog(@"NO");
return NO;
}
+ (NSURLRequest *)canonicalRequestForRequest:(NSURLRequest *)request {
NSLog(@"%@", NSStringFromSelector(_cmd));
NSMutableURLRequest *newRequest = [request mutableCopy];
// This header will not be in self.request when fetched within the -[APURLProtocol start loading] method.
[newRequest setValue:@"12345" forHTTPHeaderField:@"X-CanonicalRequestTest"];
return newRequest;
}
+ (BOOL)requestIsCacheEquivalent:(NSURLRequest *)aRequest toRequest:(NSURLRequest *)bRequest {
NSLog(@"Request is cache equivalent:");
NSLog(@"Request 1: %@", aRequest);
NSLog(@"Request 2: %@", bRequest);
return YES;
}
#pragma mark -
#pragma mark Inherited instance methods
- (void)startLoading {
NSLog(@"%@. Request: %@", NSStringFromSelector(_cmd), self.request);
NSMutableURLRequest *newRequest = [[self request] mutableCopy];
[[self class] setProperty:@"" forKey:kAPURLProtocolHandledRequest inRequest:newRequest];
[self.connection cancel];
self.connection = [[NSURLConnection alloc] initWithRequest:newRequest
delegate:self
startImmediately:YES];
}
@end
NSURLRequest+test.m (category to extend the description of NSURLRequest)
Warning : Do not do this at home. Do not override a method or property using categories. This is for quick debugging purposes only.
@implementation NSURLRequest (test)
- (NSString *)description {
NSString *dataString = [[NSString alloc] initWithData:self.HTTPBody encoding:NSUTF8StringEncoding];
return [NSString stringWithFormat:@"%@: %p {URL: %@, Method: %@, Headers: %@, Data: %@",
NSStringFromClass([self class]), self, self.URL, self.HTTPMethod, [self allHTTPHeaderFields], dataString];
}
@end