Question

I did find an answer to this title and I did do a little research but I’m still not getting the flow. Here is what I want to happen:

1) click a button on the presenter view to open a modal view. 2) retrieve some value and click a button to close the modal view….sending the value to the presentor view and execute a method.

I get that this works like a callback but I still can’t figure out where to put the callback stuff.

So, how exactly do I do this? A) In the presentViewController completion block, should I include the presenter view method to execute when modal view is completed?

Or: B) In the modal view’s dismissViewControllerAnimated completion block, should I include the presenter view method to execute when modal view is completed?

Can somebody help me with some sample code? Or at least help me get the flow of which block to put the code in?

Thank you, P

Answer 1

You talk about completion blocks so I am assuming you do not want to use delegates.

In the viewController that will be presented modally you need to provide a public completion handler, that will be called when it is dismissed.

@interface PresentedViewController : UIViewController

@property (nonatomic, strong) void (^onCompletion)(id result);

@end

Then in the implementation you need to call this completion block on dismissal. Here I assume the viewController is dismissed on a button click

- (IBAction)done:(id)sender
{
  if (self.onCompletion) {
    self.onCompletion(self.someRetrievedValue);
  }
}

Now back in the viewController that presented the modal you need to provide the actual completion block – normally when you create the viewController

- (IBAction)showModal;
{
  PresentedViewController *controller = [[PresentedViewController alloc] init];
  controller.onCompletion = ^(id result) {
    [self doSomethingWithTheResult:result]
    [self dismissViewControllerAnimated:YES completion:nil];
  }
  [self presentViewController:controller animated:YES completion:nil];
}

This will create the new viewController to be presented modally and define what needs to happen on completion.