What is Referencing outlet collection in Xcode4 Interface Builder?

The IBOutletCollection is a way to group IBOutlets. Imagine that you have 3 or 4 UILabels, on which you will apply a style (font, backgroundColour, opacity, etc). With a IBOutletCollection, it becomes trivial to do this. First you need to define your IBOutletCollection:

@property (nonatomic, retain) IBOutletCollection(UILabel) NSArray *labelsCollection;

(notice the type we are putting inside parenthesis, although we could put an id, if we had a mix collection)

Connect the IBoutlets on Interface Builder and then just iterate it:

for(UILabel *label in labelsCollection){    // Apply your styles}

Hope this helps you understand:

http://useyourloaf.com/blog/2011/3/28/interface-builder-outlet-collections.html

Ive just been hacking XIBs.

You can see a Outlet collection in use here:

A control can have multiple gesture recognizers which are stored in :

UITouch @property(nonatomic,readonly,copy) NSArray *gestureRecognizers

Open IB

Drag UITextView to a IB View.

Drag Pinch Gesture Recognizer to the textview.

Click on each in the tree of objects and open the Connections Inspector.

you'll see its been added a collection, not a single outlet.

OUTLET COLLECTIONSgestureRecognizers ------> Pinch Gesture

Using XCode Interface Builder create/connect your IBOutlets to the IBOutlet Collection. As result, you will get the following code in .h file:

@property (strong, nonatomic) IBOutletCollection(UILabel) NSArray *labels;

In the .m file you can iterate using for-loop to get your desired features like font size or color:

for (UILabel *label in self.labels) {        label.font = [UIFont systemFontOfSize:14];        label.textColor=[UIColor blueColor];}

or

@synthesize labels;...for (UILabel *label in labels) {        label.font = [UIFont systemFontOfSize:14];        label.textColor=[UIColor blueColor];}