Question

I am using Xcode 4.3 and I have a label in one view controller that I want to update the text in a text field in another view controller. How should I do this?

Answer 1

You should put the text in your model class (assuming that you have one; if you don’t, you need to create it). When the end-user edits the text field, your code should change the string in your model; when the label displays, you should read its text from the model. The easiest way of sharing your model among multiple classes is to define a singleton.

Header:

@interface Model : NSObject
@property (NSString*) labelText;
+(Model*)instance;
@end

Implementation:

@implementation Model
@synthesize labelText;
+(Model*)instance{
    static Model *inst;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        inst = [[Model alloc] init];
    });
    return inst;
}
-(id)init {
    if (self = [super init]) {
        labelText = @"Initial Text";
    }
    return self;
}
@end

Using the model:

// Setting the field in the model, presumably in textFieldDidEndEditing:
// of your UITextField delegate
[Model instance].labelText = textField.text;

// Getting the field from the model, presumably in viewWillAppear
myLabel.text = [Model instance].labelText;