How to signal when a view is done and returning? - objective-c

Question

I'm building an iphone app, and i have my first view call a second view when a button is pressed. The second view is a UIPicker with a button. When the button is pressed, I want to return the data from the UIPicker. How would i do this? Here is the code i have so far:
This is the Button that calls the subview
-(IBAction)DayView:(id)sender{
DayPickerViewController *DPView =[[DayPickerViewController alloc]
initWithNibName:nil bundle:nil];
[self presentModalViewController:DPView animated:YES];
//tried below, doesnt work
//[calc SetDay:[DPView Getrow]];
//DaysButton.titleLabel.text =#"%i",[DPView Getrow];
}
This is the pickerview's code:
-(IBAction)buttonPressed{
NSInteger row = [dayPicker selectedRowInComponent:0];
data = row;
[self dismissModalViewControllerAnimated:YES];
}

Answer 1

The approach you tried first works on Windows where you can open and close a modal dialog in a similar way that you enter and leave a function. However, iOS doesn't work like this.
The simplest approach is to add an instance variable in you second view that refers to the parent view. Then you can notify the parent view by directly calling an instance method:
Main view:
-(IBAction) dayView:(id)sender {
DayPickerViewController *dpView = [[DayPickerViewController alloc]
initWithNibName:nil bundle:nil];
dpView.parent = self;
[self presentModalViewController:dpView animated:YES];
}
-(void) viewController:(DayPickerViewController*)controller
didSelectRow:(NSInteger)row {
// the child view has been dismissed,
// do something with the selected row...
}
Child view:
#property(nonatomic, retain) WoWViewController* parent;
...
#synthesize parent;
-(IBAction) buttonPressed {
NSInteger row = [dayPicker selectedRowInComponent:0];
[self dismissModalViewControllerAnimated:YES];
[self.parent viewController:self didSelectRow:row];
}