Wait to return until object has value - ios

Question

I have a method that gets called that looks like this:
- (NSString *)getClassNamesWithClassID: (NSNumber *) classID {
NSLog(#"Gettting Name for classID: %#", classID);
NSURLRequest *classIDRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"https://dphs.edu20.org/api/get_classes_with_ids?api_key=%#&classIDs=%#", apiKey, classID]]];
NSURLConnection *classIDConnection = [[NSURLConnection alloc] initWithRequest:classIDRequest delegate:self];
return className;
}
Below this, there are all of the delegate methods for the NSURLConnection. The variable className is set in the delegate's 1connectionDidFinishLoading1 method. However, it needs to be returned in the above getClassNamesWithClassID method. When I try to call the getClassNamesWithClassID method, the method always returns nil, presumably because the NSURLConnection takes some time to receive the data and then set it to the className variable but the return is happening before all of this occurs. How can I have the method "wait" until the NSURLConnection is complete until it returns className?
EDIT
Synchronous connection code:
- (NSString *)getClassNamesWithClassID: (NSNumber *) classID {
classDataArray = [[NSMutableArray alloc] init];
NEOAPIData = [[NSMutableData alloc] init];
NSLog(#"Gettting Name for classID: %#", classID);
NSURLRequest *classIDRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"https://dphs.edu20.org/api/get_classes_with_ids?api_key=%#&classIDs=%#", apiKey, classID]]];
NSURLResponse * response = nil;
NSError * error = nil;
NSData * data = [NSURLConnection sendSynchronousRequest:classIDRequest
returningResponse:&response
error:&error];
if (data)
{
[NEOAPIData appendData:data];
NSString *strData = [[NSString alloc]initWithData:NEOAPIData encoding:NSUTF8StringEncoding];
NSLog(#"%#",strData);
classDataArray = [NSJSONSerialization JSONObjectWithData:NEOAPIData options:NSJSONReadingMutableLeaves error:nil];
return #"Hello";
}
return #"Error";
}

Answer 1

Short answer: You can't, and you shouldn't.
NSURLConnection (which is now deprecated BTW) is an async method. It returns immediately, before the network request has even been sent, much less data received.
What you need to do is refactor your getClassNamesWithClassID method to be a method that takes a completion block with the class name as a parameter to that block. Then write your code so that it saves the completion block to an instance variable and invokes it in the connectionDidFinishLoading delegate method. Then write the caller to pass in code that should be invoked once the class name is known.

Answer 2

You need call NSURLConnection synchronous like following code
- (NSString *)getClassNamesWithClassID: (NSNumber *) classID {
NSLog(#"Gettting Name for classID: %#", classID);
NSURLRequest *classIDRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"https://dphs.edu20.org/api/get_classes_with_ids?api_key=%#&classIDs=%#", apiKey, classID]]];
// NSURLConnection *classIDConnection = [[NSURLConnection alloc] initWithRequest:classIDRequest delegate:self];
NSURLResponse * response = nil;
NSError * error = nil;
NSData * data = [NSURLConnection sendSynchronousRequest:classIDRequest
returningResponse:&response
error:&error];
if (error == nil)
{
// Parse data here
return className;
}
return nil;
}