在两个UIViewController之间传递数据

Question

I need to pass data of UILabel from ViewB to ViewA. My ViewA has a UILabel with some number. This number can be changed in ViewB which I open as a new UIViewController as below:

viewB = [[SettingsViewController alloc] initWithNibName:@"SettingsViewController" bundle:nil];

ViewB also has a UILabel to hold the same value. I tried to pass this value from ViewB to ViewA by assigning UILabel's like so:

viewB.countdownLabel = self.countdownLabel;

That didn't work. Thanks for suggestions...

Answer 1

我想你想要的是： viewB.countdownLabel.text = self.countdownLabel.text

Answer 2

KVO also can be used.

http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/KeyValueObserving/KeyValueObserving.html#//apple_ref/doc/uid/10000177-BCICJDHA

Answer 3

确保viewB.countdownLabel是保留属性，并且应该可以使用。

Answer 4

By saying "viewB.countdownLabel = self.countdownLabel;" you are simply making viewB's countdownLabel a reference to the original label, you're not copying their values. You need to do the following...

[viewB.countdownLabel setText:self.countdownLabel];

Answer 5

I would suggest that you use AppDelegate to pass the value across to any viewController (and read the documentation here ).

GeneralAppDelegate*appDelegate=[[UIApplication sharedApplicaton] delegate];
myLocalProperty=appDelegate.someDataModelProperty;

or just use

viewB.countdownLabel.text = self.countdownLabel.text;

in your code.