Question

How would I go about changing the a UILabel property in another view controller?

I have #import "SecondViewController.h" imported in the FirstViewController.m file and then

I have the following in a method in FirstViewController

-(IBAction) someAction {

    SecondViewController *objV1 = [[SecondViewController alloc]init];

    objV1.secondViewControllerLabel.alpha = 0.2;

NSLog(@"someAction");

}

when someAction is called nothing happens to the UILabel in the SecondViewController.

also, in this example both first and second view controllers are in another view controller called MainViewController. So, they are both onscreen at the same time.

thanks for any help.

Answer 1

From what you tell us, it would seem that you need to set the “embeded view controllers” as childs of the parent View Controller.

[mainViewController addChildViewController:childViewController];
[childViewController.view setFrame:self.view.bounds];
[self.childContainerView addSubview:childViewController.view];
[childViewController didMoveToParentViewController:self];

This is very powerful, because you can forward IBActions from the mainViewController to their child…

[mainViewController childViewControllers]

Returns an array of them, and also take a look at

– shouldAutomaticallyForwardRotationMethods
– shouldAutomaticallyForwardAppearanceMethods

So your child get automatically informed about the rotations of their parent.

To answer your question, you could do something like:

// In Parent View Controller
- (IBAction) anAction:(id) sender
{
    for (CustomChildController *child in self.viewControllers) {
        [child handleSomeAction];
    }
}

Check out what the docs say for more details.