Question

I have two view controllers. I’m on first, and when I press the button, second view controller is pushed onto the stack of navigation controller. Here, in second view controller I have a table view and when I tap on some rows, they are selected (like checkboxes) and some data related to that rows are added to an array. Now when I’m done with selecting, I want to go back to the first view controller and use that array. How to do that? Now my app works like this: I have a delegation protocol, then object in which I have the property array, and I can access that object and its array from whole app…but I don’t really like that. Is this correct/best/simplest way to do that?

Answer 1

I have a delegation protocol, then object in which I have the property array, and I can access that object and its array from whole app…but I dont really like that. Is this correct/best/simplest way to do that?

Delegation is the correct pattern to use here, but what you describe isn’t so much delegation as it is using a global variable. Perhaps you’re storing globals in your App Delegate — generally something you can avoid if you can.

Here’s a rough outline of what the code should look like:

SecondViewController.h:

@protocol SecondViewControllerDelegate;

@interface SecondViewController;

SecondViewController : UIViewController
{
    id<SecondViewControllerDelegate> delegate;

    NSArray* someArray;
}

@property (nonatomic, assign) id<SecondViewControllerDelegate> delegate;
@property (nonatomic, retain) NSArray* someArray;

@end

@protocol SecondViewControllerDelegate
- (void)secondViewControllerDidFinish:(SecondViewController*)secondViewController;
@end

SecondViewController.m:

@implementation SecondViewController

@synthesize delegate;
@synthesize someArray;

- (void)dealloc
{
    [someArray release];
    [super dealloc];
}

- (void)someMethodCalledWhenUserIsDone
{
    [delegate secondViewControllerDidFinish:self];
}

FirstViewController.h:

#import SecondViewController

@interface FirstViewController : UIViewController <SecondViewControllerDelegate>
{
    ...
}

@end

FirstViewController.m:

@implementation FirstViewController

- (void)secondViewControllerDidFinish:(SecondViewController*)secondViewController
{
    NSArray* someArray = secondViewController.someArray
    // Do something with the array
}

@end