Waiting for an asyncronous call to finish within a completion block

Question

I am currently working on a POC app, I have previously posted about it here. I am trying to handle automatic refreshing of an authentication token should my server give me a 401

Answer 1

Assuming you can change implementation of requestAuth, add a completion handler parameter to requestAuth function.
Inside requestAuth implementation, call that handler after token is received. Then in requestDataForUser:

case 401:
     NSLog(@"401 Challenge - Retrying Authentication, Attempt %ld", (long)retryAttempts);
     [weakSelf refreshAuth withCompletionHandler:weakself.requestDataForUser];
     retryAttempts += 1;
     break;

Otherwise, use NSOperationQueue and set maximum concurrent operation to 1:

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
queue.maxConcurrentOperationCount = 1;

[queue addOperationWithBlock:^{
    [weakself requestAuth];
}];

[queue addOperationWithBlock:^{
    [weakself requestDataForUser];
}];