https://stackoverflow.com/questions/54447919/nsurlsessiondatatask-returning-nil-value-after-getting-response

Fetch.m

- (void)verifyCode:(NSString*)code {
    NSString *identifier = self.potentialPerson[@"ID"];
    NSString *urlString = [[inputModel api] stringByAppendingFormat:@"action=validate&code=%@&inputID=%@",
                     code, identifier];
    
    [self validateInputFrom:urlString completionHandler:^(NSDictionary *dictionary) {
        self.codeResponse = dictionary;
        NSLog(@"message %@", dictionary);
        
        // use `dictionary` here, but ...
    }];
    // ... do not try to use `dictionary` or `codeResponse` here
}

- (NSURLSessionDataTask *)validateInputFrom:(NSString *)url completionHandler:(void (^)(NSDictionary *))completionHandler {
    NSURLRequest *request = [NSURLRequest  requestWithURL:[NSURL URLWithString:url]];
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        NSDictionary *result = [NSJSONSerialization JSONObjectWithData:data options:0 error:NULL];
        if (completionHandler) {
            dispatch_async(dispatch_get_main_queue(), ^{
                completionHandler(result);
            });
        }
    }];
    [task resume];
    return task;
}

Also note that verifyCode now is a void return type. You cannot return a value that is set asynchronously later. Remember, you return from validateInputFrom immediately, but the completionHandler block is called later (for a network request, it may be a few seconds later).

Sorry about that my variable for codeResponse was originally camelcase from the original code. I made modifications so that I can post it on stack. Okay, that makes sense. I can only make changes to the dictionary after it has completed it's task so when verifyCode completes is when codeResponse gets updated. I apologize for any inconvenience, but I do appreciate the help you have provided. Still learning about async calls.