Question

I have a view controller, let’s call it HomeViewController, that pops up an alert view without any buttons that says “Please wait while connecting to the server”. While waiting, the view controller calls a method in another class (ServerConnection) which sends data to the server.

What I need to do is cancel that alert once I receive a server response, but it won’t work if I do the following:

HomeViewController *hvc = [[HomeViewController alloc] init];
[hvc waitAlertCancel];

//note:waitAlertCancel is a method that calls the following line of code:
[waitAlert dismissWithClickedButtonIndex:0 animated:TRUE];

What should I do to be able to cancel that alert view from another class?

Answer 1

Blocks are awesome.

---

If you need to call code in one class from another class after an event occurs, blocks are the perfect solution. Before blocks were available, you’d typically handle a design like this using a delegate pattern, which is fine, but it can be heavy-handed in situations like yours where you just need to dismiss an alert. So, using blocks is a much cleaner solution, IMO.

Create a method in your ServerConnection class that uses blocks for a callback. Something along the lines of

- (void) connectWithCompletionBlock(void(^))completionBlock;

Then you would call the connectWithCompletionBlock: method like this:

[myServerConnection connectWithCompletionBlock: ^ { [waitAlert dismissWithClickedButtonIndex:0 animated:TRUE]; }];

Once the ServerConnection object receives a server response, you can have it run the completion block.