Use a NSURLconnection for multiple posts to API - objective-c

Question

I having a situation here where I have some templates (objects), which I want to push to my backend. Now When the users presses the synchronise button, there is a connection to the backend form which I get all the templates. The templates on the IPAD app are compared to those that were transferred from the backend. If a template on the IPAD app has the ID(0), then there is a post to the backend. the backend then returns the saved template with his ID (to add to the local stored template).
Now I think my problem here is that I'm using the same connection (templateupdateconnection => bad name...) for all of those posts to the backend. The actual problem is that in the connectiondidfinishloading method, I only get a response on the last template that was posted to the backend.
Anyone who knows how I can solve this?
Thanks in advance!!
THE CODE
-(void)syncRegistrations:(NSArray *)arrayOfRegistrations{
NSFetchRequest *request = [[NSFetchRequest alloc]init];
[request setEntity:[NSEntityDescription entityForName:#"Registration" inManagedObjectContext:self.managedObjectContext]];
NSError *error;
NSArray *Data = [self.managedObjectContext executeFetchRequest:request error:&error];
BOOL old=FALSE;
for(int registrationCounter = 0; registrationCounter < arrayOfRegistrations.count; registrationCounter ++){
NSDictionary *dictRegistration = [arrayOfRegistrations objectAtIndex:registrationCounter];
for(Registration *registration in Data){
if([dictRegistration objectForKey:#"id"] == registration.id){
old = TRUE;
}
else if ([registration.id intValue]==0){
NSString *jsonRequest = [NSString stringWithFormat:#"{\"form\":%#}",registration.form.id];
NSLog(#" de jsonrequest: %#",jsonRequest);
NSURL *url = [NSURL URLWithString:#"http://mybackend/registrations"];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
NSData *requestData = [NSData dataWithBytes:[jsonRequest UTF8String] length:[jsonRequest length]];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"];
[request setValue:[NSString stringWithFormat:#"%d", [requestData length]] forHTTPHeaderField:#"Content-Length"];
[request setHTTPBody: requestData];
self.registrationtoupdate = registration;
self.registrationUpdateConnection = NULL;
self.registrationUpdateConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[self.registrationUpdateConnection start];
registration.id=[NSNumber numberWithInteger:-1];
[self.managedObjectContext save:&error];
old=TRUE;
}
}
if(old==FALSE){
//nieuwe template toevoegen
Registration *registration = [NSEntityDescription insertNewObjectForEntityForName:#"Registration" inManagedObjectContext:self.managedObjectContext];
registration.id = [dictRegistration objectForKey:#"id"];
registration.form = [self getFormByID:[dictRegistration objectForKey:#"form"]];
[self.managedObjectContext save:&error];
}
old=FALSE;
}
//[self getRC];
[self performSelector:#selector(getRC) withObject:nil afterDelay:3];
}
CONNECTIONDIDFINISHLOADING METHOD
else if([connection isEqual:self.registrationUpdateConnection]){
NSDictionary *dictRegistration = [NSJSONSerialization JSONObjectWithData:self.registrationdata options:kNilOptions error:&error];
NSLog(#"de data van de registratie is: %#",dictRegistration);
NSLog(#"de registration to update is: %#",self.registrationtoupdate);
self.registrationtoupdate.id = [dictRegistration objectForKey:#"id"];
[self.managedObjectContext save:&error];
}

Answer 1

You should encapsulate the NSURLConnection and all relevant state data into a class. Let that class have a start method which asynchronously starts the connection and a completion block which has a parameter result representing the eventual result of the request. That way, you don't mismatch response data with other connections.
Then, in the completion block, reference the corresponding context (registration to update), get the JSON representation and update the context on the correct thread or queue appropriately for the given managed object context (see below "Thread Confinement"):
So, basically:
else if ([registration.id intValue]==0) {
// setup the request
NSMutableURLRequest *request = ...
MyHTTPRequestOperation* op =
[[MyHTTPRequestOperation alloc] initWithRequest:request
completion:^(void)(id result)
{
if (![result isKindOfClass:[NSError class]]) {
assert(result != nil && [result isKindOfClass:[NSData class]]);
NSDictionary* dictRegistration =
[NSJSONSerializationJSONObjectWithData:result
options:kNilOptions
error:&error];
// Todo: check if dictRegistration has the required type
id newRegistrationID = [dictRegistration objectForKey:#"id"];
// Update the model on the thread/queue you defined for the
// NSManagedObjectContext:
[self updateRegistration:registration withID: newRegistrationID];
}
else {
// an error occurred
}
}];
[op start];
registration.id=[NSNumber numberWithInteger:-1];
}
You should be familiar with NSModelObjectContext and "Thread Confinement".
see also: -(id)initWithConcurrencyType:(NSManagedObjectContextConcurrencyType)ct
Core Data Release Notes for OS X v10.7 and iOS 5.0
Core Data Best Practices at WWDC/2012 (requires dev account)

Answer 2

#CouchDeveloper, thanks for putting me on the right track!!
The final solution, wasn't to create a subclass of the NSURLConnection, but just using the completion block in combination with a simple NSURLConnection. check the following code:
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if ([data length] > 0 && error == nil){
NSDictionary *dictrc = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
NSLog(#"de data van de rc is: %#",dictrc);
rc.id = [dictrc objectForKey:#"id"];
[self.managedObjectContext save:&error];
}
}];