AFNetworking : Handling of asynchronous get request with AFJSONRequestOperation

Question

I have the following code inside a class (static method) which I call to get data from an API. I decided to make this a static method just so I can reuse it on some other parts of the app.

+ (NSArray*) getAllRoomsWithEventId:(NSNumber *)eventId{

    NSURL *urlRequest = [NSURL URLWithString:[NSString stringWithFormat:@"http://blablba.com/api/Rooms/GetAll/e/%@/r?%@", eventId, [ServiceRequest getAuth]]];

    NSMutableArray *rooms = [[NSMutableArray alloc] init];

    NSURLRequest *request = [NSURLRequest requestWithURL:urlRequest];

    AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
        NSLog(@"Response of getall rooms %@", JSON);


        NSArray *jsonResults = (NSArray*)JSON;
        for(id item in jsonResults){
            Room* room = [[Room alloc]init];
            if([item isKindOfClass:[NSDictionary class]]){
                room.Id = [item objectForKey:@"Id"];
                room.eventId = [item objectForKey:@"EventId"];
                room.UINumber = [item objectForKey:@"RoomUIID"];
                [rooms addObject:room];
            }
        }
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON){
        NSLog(@"Error");
     }];

    [operation start];
    [operation waitUntilFinished];

    return rooms;
}

Now my issue is, whenever I call this in a ViewController (ViewDidLoad method). The static method will run till the end and will return null on the rooms, but the Nslog will display the "Success" block Nslog a few seconds after. Now I understand that this is asynchronous so it doesn't wait for the success block to execute before it reaches the "return rooms;" line. With all that said, I need some advice as to how to handle this, like maybe a progress bar or something like that? Or something that delays it? I'm not really sure if that's the reight way or if it is, I am not sure how to do it.

Any advice is very much appreciated. Thank you!

Answer 1

AFNetworking is built around asynchronicity—starting a request, and then executing some piece of code once that request has finished.

waitUntilFinished is an anti-pattern, which can block the user interface.

Instead, your method should have no return type (void), and have a completion block parameter that returns the serialized array of rooms:

- (void)allRoomsWithEventId:(NSNumber *)eventId block:(void (^)(NSArray *rooms))block { // ... }

See the example app in the AFNetworking project for an example of how to do this.

Answer 2

You can write your method following way:

+ (void) getAllRoomsWithEventId:(NSNumber *)eventId:(void(^)(NSArray *roomArray)) block
{

    NSURL *urlRequest = [NSURL URLWithString:[NSString stringWithFormat:@"http://blablba.com/api/Rooms/GetAll/e/%@/r?%@", eventId, [ServiceRequest getAuth]]];

    NSMutableArray *rooms = [[NSMutableArray alloc] init];

    NSURLRequest *request = [NSURLRequest requestWithURL:urlRequest];

    AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
        NSLog(@"Response of getall rooms %@", JSON);


        NSArray *jsonResults = (NSArray*)JSON;
        for(id item in jsonResults){
            Room* room = [[Room alloc]init];
            if([item isKindOfClass:[NSDictionary class]]){
                room.Id = [item objectForKey:@"Id"];
                room.eventId = [item objectForKey:@"EventId"];
                room.UINumber = [item objectForKey:@"RoomUIID"];
                [rooms addObject:room];
            }
        }
        block(rooms);
    } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON){
        NSLog(@"Error");
        block(nil); //or any other error message..
     }];

    [operation start];
    [operation waitUntilFinished];

}

you can call this method like followings:

[MyDataClass getAllRoomsWithEventId:@"eventid1":^(NSArray *roomArray) {
      NSLog(@"roomArr == %@",roomArray);
    }];