How to manipulate IBOutlet UIImageView objects in series using For Loop - ios7

Question

# of Images are placed in a View using Storyboard.
I want to manipulate them programmatically using a For loop. But couldn't find how to?
Currently i am using the following code:
#property (weak, nonatomic) IBOutlet UIImageView *img_level2;
#property (weak, nonatomic) IBOutlet UIImageView *img_level3;
#property (weak, nonatomic) IBOutlet UIImageView *img_level4;
#property (weak, nonatomic) IBOutlet UIImageView *img_level5;
#property (weak, nonatomic) IBOutlet UIImageView *img_level6;
#property (weak, nonatomic) IBOutlet UIImageView *img_level7;
...
...
...
_img_level2.image = [_img_level2.image convertToGrayscale];
_img_level3.image = [_img_level3.image convertToGrayscale];
_img_level4.image = [_img_level4.image convertToGrayscale];
_img_level5.image = [_img_level5.image convertToGrayscale];
_img_level6.image = [_img_level6.image convertToGrayscale];
_img_level7.image = [_img_level7.image convertToGrayscale];
Now instead of writing them line by line i want to use a for loop. Because this procedure might be called multiple times for sizing and positioning.
Please advice, thanks!

Answer 1

Instead of having each of the buttons as its own UIButton property, you can define an outlet collection, which is essentially an array that you'll be able to treat exactly as you want (for example, loop over all of its items).
How do you do that? Simple:
In your code, replace all of the IBOutlet UIImageView... lines with:
IBOutletCollection(UIImageView) NSMutableArray *imgLevels;
On InterfaceBuilder, give each of your UIImageViews a different tag that will match its index in the IBOutletCollection.
And, finally, when you connect the objects on your .xib or storyboard file, you'll notice it will appear on the Referencing Outlet Collections section instead of the Referencing Outlets as you're used to.
Now you have an array that you can use to loop over your IBOutlets exactly as you would loop a "regular" NSArray. Good Luck!