I couldn't find a reasonable answer so i'll ask for this specific case.
I must perform a http call (setting a specific header as a token value) and parse the returned json. The json can both return a "operation completed" message or a "token expired" message.
In case of token expired i must execute another http call which will provide me the refreshed token, set the token as header and re-execute the original http call.
I decided to adopt this solution: from the main thread, i'm gonna create another thread using
...
dispatch_async(feedQueue
...
and in this thread i'm gonna performing the above descripted calls as synchronous calls using
...
[NSURLConnection sendSynchronousRequest:urlRequest
...
and only at the end of the flow i call the main thread passing results to a block.
This way code is simple, easy to read, it has a linear flow, it is completely scoped inside a unique thread, and i don't mess with delegates and different "finite-states" to manage calls chain.
But i'm not sure if this is the best approach for my specific use-case as i've read similar questions where people suggest to adopt asynchronous calls, using both finite-states or NSOperation instances, but it seems to me that both these approaches based on asynchronous calls, are not the best solutions for a http calls chain.
What is the best approach? How can i correctly implement a chain of http call?
The correct way to set this up would be to use asynchronous calls for NSURLConnection. In the connectionDidFinishLoading you will intercept the connection that just finished and launch the next chained http connection.
Setup a private variable called _connection1;
So basically, you will do something like this
NSURLRequest * request1 = ...
_connection1 = [[NSURLConnection alloc] initWithRequest:request1 delegate:self];
In the
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
if([connection isEqual:_connection1]){
NSURLRequest *request2 = ...
_connection2 = [NSURLConnection...]
}
if([connection isEqual:_connection2]){
NSURLRequest *request3 = ...
_connection2 = [NSURLConnection...request3 ]
// And so on ....
}
}
Related
Is it possible to force response caching if it contains neither Expires or Cache-Control: max-age?
I've came across this article, but unfortunately URLSession:dataTask:willCacheResponse:completionHandler: never gets called in my AFHTTPSessionManager subclass.
Any help appreciated.
You can force the caching by implementing your own NSURLProtocol that does not follow the standard HTTP caching rules. A complete tutorial is here, which persists the data using Core Data, but the basic steps are:
Subclass NSURLProtocol
Register your subclass with +registerClass:
Return YES in your +canInitWithRequest: method if this is the first time you've seen request, or NO if it isn't
You now have two choices:
Implement your own cache storage (in which case, follow the tutorial linked above)
Inject the cache control headers that you wish the URL loading system to follow
Assuming you want #2, override connection:didReceiveResponse: in your protocol subclass to create a response that has the cache control headers you want to emulate:
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response {
// Create a dictionary with the headers you want
NSMutableDictionary *newHeaders = [response.allHeaderFields mutableCopy];
newHeaders[#"Cache-Control"] = #"no-transform,public,max-age=300,s-maxage=900";
// Create a new response
NSHTTPURLResponse *newResponse = [[NSHTTPURLResponse alloc] initWithURL:response.URL
statusCode:response.statusCode
HTTPVersion:#"HTTP/1.1"
headerFields:newHeaders];
[self.client URLProtocol:self
didReceiveResponse:newResponse
cacheStoragePolicy:NSURLCacheStorageAllowed];
}
This will cause the response to be cached as if the server had provided these headers.
For URL sessions only, you need to set the session configuration's protocolClasses. Since you're using AFNetworking, that looks like:
[AFHTTPSessionManager sharedManager].session.configuration.protocolClasses = #[[MyURLProtocol class]]
There are some caveats, so make sure you read the protocolClasses documentation.
A few notes:
If there's any way to fix this by having your server send the appropriate headers, please, please do that instead.
For the sake of brevity I hardcoded "HTTP/1.1", but technically you should pull this out of the response.
AFNetworking uses the standard URL Loading System, and is mostly unrelated to this issue.
I have a project which you can imagine is like the Facebook app and I'm having trouble grasping how to organize it with RestKit and handle tokens since I'm a RestKit beginner.
This is what I got so far:
Core Data NSManagedObject classes, for each of them I added a category called REST that has functions to provide RKObjectMapping and RKRouteSet
custom RKObjectManager subclass which handles setting up headers, MIME types, setting authorization headers and Core Data stores
RKObjectRequestOperation subclass
If you have organizational advice shoot, but my main question is how do I implement automatic token refreshing after recieving a 401 HTTP status code and firing the failed request again with a fresh token?
I started by overriding the metod in my RKObjectRequestOperation subclass:
- (void)setCompletionBlockWithSuccess:(void ( ^ ) ( RKObjectRequestOperation *operation , RKMappingResult *mappingResult ))success
failure:(void ( ^ ) ( RKObjectRequestOperation *operation , NSError *error ))failure
So now I can intercept a 401 response, but now I have to make another call to refresh the token and then re-enqueue the failed operation with a fresh token, please advise how to do that.
I generally wouldn't use a custom RKObjectRequestOperation if you are using an object manager. I'd handle it at the object manager level.
In the object manager you can override each of the main request methods (which are supplied with success and failure blocks). You can implement these methods to call super but substituting the success and failure blocks with new versions which add some logic before calling the supplied versions.
Now, the additional logic would be a check of the response status. If it shows a token refresh is required it can be actioned and then the object manager can trigger a new load, using the parameters supplied in the first request.
Also, you shouldn't re-queue an operation unless the documentation states that it is supported as some operations won't work the second time they're executed...
I'm loading certain images from a certain server asynchronously. I'm firing a number of requests at once using NSURLConnection connectionWithRequest method and receive the data using NSURLConnectionDelegate didReceiveData.
At didReceiveData, how do I know which request this data matches? At didReceiveResponse I can use the URL method of the response given as a parameter, but in didReceiveData I only have the received data.
It seemed like the perfect answer would be to use NSURLConnection sendAsynchronousRequest, as the completion handler has all the required parameters: (NSURLResponse*, NSData*, NSError*). I can use [response URL] to make a match to the original request... except in one case: not all the images I try to download exist. In that case, the request is redirected to a generic error page and the URL of that generic page is received, so I can't match the response to a request I've made. This I could handle with connectionWithRequest, but I can't get the best of both worlds.
In
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
you can use
NSURLRequest *request = [connection originalRequest];
to get the request that the connection was started with.
(This method is available since iOS 5.0, but I could not find it in my Xcode iOS 5.1 Library. You find it in the iOS 6 Library, in the header file NSURLConnection.h or here: http://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSURLConnection_Class/Reference/Reference.html#//apple_ref/occ/instm/NSURLConnection/originalRequest).
More methods to manage multiple connections can be found in this thread: Managing multiple asynchronous NSURLConnection connections.
If you use sendAsynchronousRequest:queue:completionHandler: then you can just use the request parameter in the completion block.
At connection:didReceiveData: the first parameter is the NSURLConnection instance. So I don't understand where the problem is. You create a connection, then you send a request to that connection and the delegate receive the connection:didReceiveData with the connection value.
If you are using the same delegate for all the request you have to check the connection so you can say which request is associated to.
Perhaps you have to maintain a table of connection/request pairs.
I am trying to connect my iOS app to a GET data from my web service everytime something changes. My current implementation is to use NSTimer and do a ASIHttpRequest but I don't like that polling implementation. Is there a better way to do it?
I am considering starting the request and lets it keep trying until the web service status code turns to OK (status 200) or perhaps a status code of "modified". How would I do this in a view controller?
Here is what I have so far:
self.asiRequest = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:self.barcodeUrl]];
[self.asiRequest setDelegate:self];
[self.asiRequest startAsynchronous];
[self.asiRequest addRequestHeader:#"Accept" value:#"application/json"];
[self.asiRequest addRequestHeader:#"Content-Type" value:#"application/json"];
int statusCode = [self.asiRequest responseStatusCode];
I know that if the request is successful, the delegate method - (void)requestFinished:(ASIHTTPRequest *)request
I guess my question is, how do I keep an open ASIHttpRequest such that when the web service returns "modified", it calls a GET request and then keep an open connection again? This has to be asynchronous and not running on a UI thread as I don't want to keep my app hanging.
Thanks much!
The easiest way to do this without having to do much on the client-side is to get your web service to send a Location: header through when it returns "modified", pointing to the URL you want to GET with the new content. If the URL to monitor is different depending on e.g. user ID or the area of the app you are in, make a monitor script where you can pass in GET params to configure what exact URL should be returned to you when "modified" is returned.
The ASIHTTPRequest will then automatically GET the content at the new Location: and you can reschedule it in requestFinished: to the monitor URL again, knowing that the response (if not empty/"Not Modified") will ALWAYS be new data since the redirect to new data happens behind-the-scenes.
I am looking forward for posting some data and information on the web server through my iPhone application. I am not getting the way to post data to the web server from iPhone sdk.
It depends in what way you want to send data to the web server. If you want to just use the HTTP POST method, there are (at least) two options. You can use a synchronous or an asynchronous NSURLRequest. If you only want to post data and do not need to wait for a response from the server, I strongly recommend the asynchronous one, because it does not block the user interface. I.e. it runs "in the background" and the user can go on using (that is interacting with) your app. Asynchronous requests use delegation to tell the app that a request was sent, cancelled, completed, etc. You can also get the response via delegate methods if needed.
Here is an example for an asynchronous HTTP POST request:
// define your form fields here:
NSString *content = #"field1=42&field2=Hello";
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:#"http://www.example.com/form.php"]];
[urlRequest setHTTPMethod:#"POST"];
[urlRequest setHTTPBody:[content dataUsingEncoding:NSISOLatin1StringEncoding]];
// generates an autoreleased NSURLConnection
[NSURLConnection connectionWithRequest:request delegate:self];
Please refer to the NSURLConnection Class Reference for details on the delegate methods.
You can also send a synchronous request after generating the request:
[NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
If you pass a NSURLResponse ** as returning response, you will find the server's response in the object that pointer points to. Keep in mind that the UI will block while the synchronous request is processed.