Xcode 4.2和Storyboard，如何从另一个类访问数据？

Question

I was wondering how I could access data from another class using Xcode 4.2 and Storyboard? Say for instance how would I access the text of a text field from another class? Google hasn't helped and the lesson on MyCodeTeacher.com about this is outdated and doesn't work anymore...

Thanks for bearing with me!

-Shredder2794

Answer 1

Not sure if this is the only or best way, but you can create a property in the destination view's .h file and set it to a value before the segue is performed

in the destination view controller's .h file:

@interface YourDestinationViewController : UIViewController
{
    NSString* _stringToDisplay;
    //...
}
    @property (nonatomic, retain) NSString* stringToDisplay;        
    //...

and in the presenting view's .m file

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    YourDestinationViewController*viewController = segue.destinationViewController;
    viewController.delegate = self;
    viewController.stringToDisplay = @"this is the string";
}

Then you can do what you want with the property in whichever of the viewWillAppear/viewDidLoad/viewDidAppear/etc. methods best suits your purpose in the destination view's .m file

And then to check if it works, in the destination view controller's .m file:

-(void)viewWillAppear:(BOOL)animated
{
    NSLog(@"self.stringToDisplay = %@", self.stringToDisplay);
    ...
    //and if a label was defined as a property already you could set the 
    //label.text value here
}

Edit: Added more code, and made it less generic

Answer 2

This isn't specific to Storyboard. There are several ways to do what you are trying to do. You could declare a variable in your AppDelegate (an NSString) and set that in your first class. Then in your second class access the AppDelegate variable and use that to set your label. The code to do this is:

AppDelegate *appDelegate = (AppDelegate*)[[UIApplication sharedApplication] delegate];
label.text = appDelegate.myString;

Another way to do it (probably the easiest) is to declare an NSString in your second class. Then in your first class, before you push the second view set that string variable. Something like this:

MyViewController *vc = [[MyViewController alloc] initWithNibName:@"" bundle:nil];
vc.myString = @"";

The third way to do this is using delegates. This is the most 'complicated' way but is the best. You would create a delegate which gets called when your second view appears. The delegate could then return the value from the first class to you.

You may also be able to use the new completion handler block on the iOS 5 pushViewController: method.

Edit:

Custom init method:

- (void)initWithNibName:(NSString *)nibName bundle:(NSString *)bundle string:(NSString *)myString

And then when you are pushing the view just class this method and set the string through it.