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iOS

Posted by Sai Kiran Dasika
Sai Kiran Dasika
Courses Plus Student 7,278 Points

Class methods problem

Hey guys, I was recent making a small app and I ran into this massive problem where I don't have any idea what's happening. This problem is that there is an method that has a return type of a NSDictionary this dictionary is returned as the serialised version of the JSON data. The code for the problem is attached below.

View will appear code:-

-(void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:YES animated:YES];
    self.tabBarController.tabBar.hidden = NO;

    NSDictionary *dictionary = [self getProductForCategory:2];
    NSLog(@"%@", dictionary);

}

//Method that i was taking about code:-
- (NSDictionary *)getProductForCategory:(int)category
{
        static NSDictionary *returnDictionary = nil;
        NSURLSession *session = [NSURLSession sharedSession];
        NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"http://example.com/GetProduct.php?cat=%d", category]];
        NSURLRequest *request = [NSURLRequest requestWithURL:url];
        NSURLSessionDownloadTask *task = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {
            if (!error) {
                NSData *data = [[NSData alloc] initWithContentsOfURL:location];
                NSDictionary *response = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];

                    returnDictionary = [[NSDictionary alloc] initWithDictionary:response];
                //NSLog(@"%@", returnDictionary);
            }
            else
            {
                NSLog(@"Error: \n %@", error);
            }
        }];
    [task resume];
    return returnDictionary;
}

1 Answer

Michael Hulet
Michael Hulet
47,913 Points
Michael Hulet
Michael Hulet
47,913 Points

The problem is that your download task where you get the dictionary data from whatever server you're using runs asynchronously, which means the rest of your method moves on before it's done. That means when your method returns returnDictionary, returnDictionary hasn't been set to the JSON data yet, and is still nil

Sai Kiran Dasika
Sai Kiran Dasika
Courses Plus Student 7,278 Points

How do i get out of this problem ?