iOS: using async - ios

Question

I currently have a screen with 2 tables. I'm getting the data synchronously and putting it on the screen. Code looks something like:
viewController.m
DBAccess_Error_T = [getList:a byCompanyID:1];
DBAccess_Error_T = [getList:b byCompanyID:2];
[self putListAOnScreen];
[self putListBOnScreen];
DBAccess.m
+ (DBAccess_Error_T)getList:(NSMutableArray*)a byCompanyID:(NSInteger)cID
{
// Pack this up in JSON form
[self queryDB:postData];
// Unpack and put it into variable a
}
+ (id)queryDB:(id)post
{
// Send request
// Get back data
}
I'm now trying to switch this over to async and I'm struggling. It's been hard even with website tutorials and documentations.
Since all of my database utilities are in separate files from the viewControllers, I'm not sure how I can use the didReceiveData and didReceiveResponse handlers. Also, since I have 2 arrays to fill for my 2 tables, how do I distinguish the difference in didReceiveData?
Instead, what I'm trying to do now is use sendAsynchronousRequest, but it seems I need to create an unpack function for every send function...let me know if I'm way off here...it looks something like:
viewController.m stays the same
DBAccess.m
+ (DBAccess_Error_T)getList:(NSMutableArray*)a byCompanyID:(NSInteger)cID
{
NSDictionary *post = /*blah blah*/
[self queryDB:post output:(a)];
}
+ (id)queryDB:(id)post output:(id)output
{
NSError *error;
NSData *jsonPayload = [NSJSONSerialization dataWithJSONObject:post options:NSJSONWritingPrettyPrinted error:&error];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
[theRequest setHTTPMethod:#"POST"];
[theRequest setHTTPBody:jsonPayload];
[NSURLConnection sendAsynchronousRequest:request
queue:[[NSOperationQueue alloc] init]
completionHandler:^(NSURLResponse *response,
NSData *data,
NSError *error)
{
if ([data length] >0 && error == nil)
{
[self unpackDataForList:output data:data]; // This function needs to be different depending on which function called queryDB...the data will be unpacked in a different way
}
}
}
+ (void)unpackDataForList:(id)output data:(NSData*)data
{
// Do my unpacking here and stick it into 'output'.
}
How can I call a different unpackData function? are function pointers the right way to do this? Is this approach way off? Any tips would be greatly appreciated!

Answer 1

Have you ever looked at ASIHTTPRequest? It makes your life a lot easier by allowing you to use blocks. Here's an example of how to make an asynchronous request:
- (IBAction)grabURLInBackground:(id)sender
{
NSURL *url = [NSURL URLWithString:#"http://allseeing-i.com"];
__block ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setCompletionBlock:^{
// Use when fetching text data
NSString *responseString = [request responseString];
// Use when fetching binary data
NSData *responseData = [request responseData];
}];
[request setFailedBlock:^{
NSError *error = [request error];
}];
[request startAsynchronous];
}
You can find more information here:
http://allseeing-i.com/ASIHTTPRequest/