avoid duplicate HTTP requests with AFNetworking - ios

Question

I would like to find out if it's possible to avoid duplicate HTTP requests with AFNetworking. Specifically, my app may generate multiple HTTP requests which all have the same url. I would like to prevent AFNetworking from processing duplicates of the same url.
Im not sure if this can be done in AFNetworking or the underlying iOS sdk. I understand that i could manually keep trac of pending url request and avoid duplicates that way, but was wondering if there is a lower level functionality already available to take care of this.
Thanks.

Answer 1

Your best bet is to subclass AFHTTPRequestOperationManager's HTTP request operations and keep track of them there if you want to track requests the same way for each request, otherwise the logic will need to be elsewhere.
AFNetworking doesn't support this because there is probably some logic relevant to when you should and when you should not execute a duplicate request, which would be highly customizable (not generic enough for the framework)

Answer 2

I made a category that checks for in-progress GET requests before making new ones.
https://github.com/NSElvis/AFHTTPSessionManager-AFUniqueGET
It does this by using the method getTasksWithCompletionHandler of the session.

Answer 3

I had the same problem. I have a chat-application and I need to show user avatar for each message. So I made few same requests and I've resolved this issue.
First, I add NSDictionary with NSString avatar URLs keys and completion blocks objects:
#property (strong, nonatomic) NSMutableDictionary* successBlocksDictForGetAvatar;
And here's my method to get user avatar image:
- (void)getAvatarForUser:(ETBUser*)user
completion:(void(^)())completionBlock
{
if (user.avatarURL)
{
NSURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:user.avatarURL]];
if (self.successBlocksDictForGetAvatar[user.avatarURL])
[self.successBlocksDictForGetAvatar[user.avatarURL] addObject:completionBlock];
else
{
NSMutableSet* set = [[NSMutableSet alloc] initWithObjects:completionBlock, nil];
[self.successBlocksDictForGetAvatar setObject:set forKey:user.avatarURL];
AFHTTPRequestOperation* operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
UIImage* avatarImage = [UIImage imageWithData:responseObject];
if (avatarImage)
{
user.avatar = avatarImage;
[[DataManager shared] saveAvatar];
[((NSSet*)self.successBlocksDictForGetAvatar[user.avatarURL]) enumerateObjectsUsingBlock:^(void(^successBlock)(), BOOL *stop) {
successBlock();
}];
[self.successBlocksDictForGetAvatar removeObjectForKey:user.avatarURL];
}
}
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
[self.successBlocksDictForGetAvatar removeObjectForKey:user.avatarURL];
}];
[self.manager.operationQueue addOperation:operation];
}
}
}
Here I check if my dictionary contains request. If YES, I add completion block for user in dictionary. Otherwise I setObject:forKey: and make AFNetworking request. In success and fail blocks I clean my dictionary.
P.S. Here's my manager getter:
- (AFHTTPRequestOperationManager*)manager
{
if (!_manager)
{
_manager = [[AFHTTPRequestOperationManager alloc] initWithBaseURL:kBaseURL];
[_manager.requestSerializer setValue:NetworkConstantsHeaderAcceptValue forHTTPHeaderField:NetworkConstantsHeaderAcceptKey];
[_manager.operationQueue setMaxConcurrentOperationCount:1];
}
return _manager;
}