breaking up an API connection call into functions Objective-C - objective-c

Question

This most likely a very trivial questions but I have a connection set up to an API in order to retrieve information. Right now I have everything setup in viewDidLoad. I know there is a more efficient way to place this information for later access by the user but I am too inexperienced in Objective-C to know how to do it. Here is how I have it all laid out at the moment.
NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:#"https://www.myurl.com"]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
NSData *myResponse = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:nil error:nil];
NSString *myString = [[NSString alloc] initWithData:myResponse encoding:NSUTF8StringEncoding];
SBJsonParser *myParser = [[SBJsonParser alloc] init];
NSArray *myData = [parser objectWithString:myString error:nil];

Answer 1

Try this:
- (void)loadAndParseURL:(NSString *)URLString
completion:(void (^)(NSArray *data))completion {
NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:URLString]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
dispatch_async(dispatch_get_global_queue(DISPATH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData *myResponse = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:nil error:nil];
NSString *myString = [[NSString alloc] initWithData:myResponse encoding:NSUTF8StringEncoding];
SBJsonParser *myParser = [[SBJsonParser alloc] init];
NSArray *myData = [parser objectWithString:myString error:nil];
completion(myData);
});
}
completion is a block (anonymous function pointer), which accepts an array as parameter and executes customized code blocks. The block holds the value of local variables, aka the 'environment', and evaluates its content at the time of execution(, usually with delay of some kind), in this example, after myData is parsed from myString. dispatch_async puts the anonymous block that sends the request and does other stuff onto a background queue (in a background thread, of course). So the calling to this method is returned before the response is even received, and you should arrange anything after within the completion block.

Answer 2

If spinning it off into a thread is what you are looking for I would use sendAsynchronousRequest
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:URLString]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
NSString *myString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
SBJsonParser *myParser = [[SBJsonParser alloc] init];
NSArray *myData = [parser objectWithString:myString error:nil];
// Do what you want with the response and subscribe
//anywhere in your code to get notified when it completed.
[[NSNotificationCenter defaultCenter]
postNotificationName:#"NotifyMeWhenDone"
object:self];
}];