Outlet Collections

A quick post to explain my tweet.

TL;DR: I can batch show and hide UIViews really easily now. Easier than setting up a bunch of outlets, fiddling with tags, making dummy views, or groveling through the view hierarchy.

I bet it’s Cocoa 101 nowadays, but they were new to me, pretty much seeing the reference when dragging a connection to header files (which I never do) and promptly forgetting about them. I might have seen reference to them in a WWDC sessions or something. But finally now I had a real use. Yay! For a lot of this stuff I need to actually use it for Something Real before it sticks in my brain. I can learn stuff by doing, but I’m lousy at memorization. Just look at my history grades during high school. On second thought, please don’t.

RideBuddy™ is one of the new apps coming from Cycling Fusion. Amongst a ton of other stuff, RideBuddy lets you track workout time in various heart zones – ranges of heart rates that have different benefits and consequences to the body. We like the Sally Edwards Heart Zones® system, which is a five-zone system based on certain physiological markers. I won’t get into specifics here, you can join the Cycling Fusion Winter Training in January and get the full details.

Five zones are kind of a lot for a beginner or just a casual rider to wrap their mind around, so Sally created Zoning™, a friendlier three-zone system and a color-coded heart rate monitor. It’s only three zones, but it’s based on the same physiological markers as the five-zone system. You can get a lot of health and training benefit by using the three zone system, and can graduate to the five-zone system when you feel up to it.

My stuff needs to support both. So, I have a number of screens like this one:

Something that’ll support three zones or five zones. Internally I can support from one to five zones. The code that adjusts the layouts based on the zone system in-use hides everything zone-related, then populates and enables stuff zone-by-zone until it runs out of zones. In the above screenie I have four objects per zone: two static labels and two text fields. zone zone zone.

To simplify that work, I have five IBOutletCollection(UIView)s — one for each zone. I walk through all of them to Hide All The Things, then walk the zones enabling a particular collection and populating items until I run out of zones. If I don’t hit a collection, it stays hidden.

Understandably, this is so much nicer than setting up an IBOutlet for each label and text field and making the connections. Or setting a tag on the items. Or groveling through the view hierarchy showing and hiding things. Or having a dummy UIView just to be a container. Just add the outlet collection and make connections in IB.

Markus Möller on Twitter “uses them for animating / moving groups of views. Better than putting them all in a container view. Less hierarchy.” which is another excellent use.