Passing data from UIViewController to 1 back UIVie

问题:

So I have this UINavigationController, I'm on the first moving to the next view, than I want to hit the 'back' button and to go back to the first view with the data that I saved into 'strAddress' on the second view. I want to present the data on the first view on 'lblShowStr.text'.

how can I manage to do that? I've searched all the web, found some people that wrote, but couldn't understand what they have been told there.

Thanks!

回答1:

In your first view controller you might have an NSString property called strAddress. and you put that string into lblShowStr.text every time the view appears.

In your second view controller you might have a property pointing to an instance of view controller one. When you instantiate your second view controller you could assign the property on it to the first view controller.

secondViewController.firstViewController = self; or [secondViewController setFirstViewController:self];

Then when the user presses the back button viewDidAppear would get called for the first view and update the string.

I am assuming you don't want to store this data anywhere else e.g. in your model or nsuserdefaults etc.

回答2:

You can get a reference to the previous viewController in your navigation stack by saying:

NSArray *viewControllers = self.navigationController.viewControllers;
MyViewControllerClass *previousController = [viewControllers objectAtIndex:[viewControllers count] - 2];

You can then set a property on the 'previous' view controller to store your text, or even set the label outlet's text directly like this:

previousController.lblShowStr.text = self.strAddress;

It's not the best way to do it (the best way involves creating a custom delegate protocol or using NSNotificationCenter) but it's the easiest way.