Change an UIImageView's alpha and show from UIActionSheet - objective-c

Question

In my UIActionSheet I have a button which mark the touched array as favorite. When an array is favorite, I have a star that shows before the array's name. The favorite icon has an alpha 0, and by touching the "Add as Favorite" button the alpha changes to 1. The arrays are located inside an UIViewController, which shows 1 array in each cell.
The problem I have is that I have to reopen the ViewController for the star to show.
How can I fix so the star shows immediately when I press the "Add as Favorite" button, without reopening the ViewController?
The Favorite Icons alpha is updated under:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
And this is the code that updated the alpha:
if ([FavoriteArray containsObject: [mainArray objectAtIndex:indexPath.row]])
{
favoriteImage.alpha = 1;
}
Thanks!

Answer 1

You need to monitor when the action sheet has been actioned on, and update the collection view accordingly. An example implementation is as follows:
UIActionSheet* actionSheet = ...;
// Set yourself as the action sheet delegate, so you can monitor when events occur
actionSheet.delegate = self;
...
// This is called when a user selects an item within the action sheet
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
// kFavouriteButtonIndex is the index of the action sheet item to favourite
if (buttonIndex == kFavouriteButtonIndex) {
// Reload your collection view to update the cells
[self.collectionView reloadData];
}
}
Instead of calling reloadData, if you know the indexPath of the item which is being favourited, then you can call reloadItemsAtIndexPaths:#[indexPath] to make the process more efficient.

Answer 2

You will want to update the image's alpha when a button is selected. You can do this by implementing the UIActionSheetDelegate protocol in your UIViewController. You can do this in you View Controller's .m file:
#interface MyViewController : UIViewController <UIActionSheetDelegate>
Then override the actionSheet:clickedButtonAtIndex: method in the .m file:
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex{
//make sure that the button pressed is the one which should change the image alpha:
if(buttonIndex == 2){ //put the button index in the place of "3"
//your code to update the alpha here
}
}
Make sure that you set the UIActionSheet's delegate to self:
myActionSheet.delegate = self;