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iOS Build a Playlist Browser with Objective-C Refactoring Our Code Tapping On Our Playlists

Stepan Ulyanin
Stepan Ulyanin
11,318 Points
Posted by Stepan Ulyanin
Stepan Ulyanin
11,318 Points

How come the IBOutletCollection gives the index to the UIImageView that corresponds to our model (playlist)?

So we add the UIImageViews to the IBOutletCollection and they get some index assigned because the IBOutletCollection is an NSArray, what is the principle behind that? I remapped the UIImageView's in different order to the IBOutletCollection -> the icons changed too, so there is some connection between those (model and the view), I just can't connect it in my mind?

2 Answers

eirikvaa
eirikvaa
18,015 Points

From a NSHipster post: The order of an outlet collection appears to be roughly the order in which their connections are established in Interface Builder. However, there are numerous reports of that order changing across versions of Xcode, or as a natural consequence of version control. Nonetheless, having code rely on a fixed order is strongly discouraged.

Seems you can't be guaranteed a fixed order with IBOutletCollection.

Stepan Ulyanin
Stepan Ulyanin
11,318 Points
Stepan Ulyanin
Stepan Ulyanin
11,318 Points

Thanks for your answer but I think this is the part I can't understand: Pasan creates the IBOutletCollection of (UIImageView) and then in the implementation file he does this:

UIImageView *playlistImageView = self.playlistImageViews[i];

where playlistImageViews is the IBOutletCollection obviously, I can't understand the logic behind this assignment, intuitively I would do something like:

UIImageView *playlistImageView;

playlistImageView.image = "whatever UIImage there is";
self.playlistImageViews[i] = playlistImageView;

But I know that elements of NSArray are immutable:/ Sorry for all this questions, just want it to make sense to me

eirikvaa
eirikvaa
18,015 Points

It doesn't make any sense doing it the way you proposed, because I guess you would just overwrite the UIImageView object in the self.playlistImageViews array with the newly created playlistImageView object. You want to get and use the UIImageView object from the playlistImageViews array, so you assign it to the playlistImageView object.

Stepan Ulyanin
Stepan Ulyanin
11,318 Points
Stepan Ulyanin
Stepan Ulyanin
11,318 Points

// icon from playlist[0] -> playlistImageView.image that stores the UIImageView object from the IBOutletCollection with the index 0

That is where the binding happens; ok, it finally made sense, thank you for your patience

Tam Pham
Tam Pham
3,203 Points
Tam Pham
Tam Pham
3,203 Points

You can do like this and it still works:

((UIImageView*)self.playlistImageViews[index]).image =playlist.playlistIcon; ((UIImageView*)self.playlistImageViews[index]).backgroundColor =playlist.backgroundColor;

The reason this statement: UIImageView *playlistImageView = self.playlistImageViews[i] works because playlistImageView is a pointer to an object in the array self.playlistImageViews. So when you do like playlistImageView.image = some image, you're actually doing self.playlistImageViews[i].image = some image.