Efficiency of create views programmatically vs IB

Question

I have a large number of UIViews that are created in the app delegate applicationDidFinishLaunching and added to an NSMutableArray. The user pages through these views using a page control and scroll view. I created the UIView and its child components in IB. They are wired to a controller. To create 170 views on the iPhone takes about 30 seconds. Eventually, I'll have over 1000 views. Besides being slow, it will also kill the app because of memory use. How much faster and memory efficient is creating everything programmatically without views? How might some of the 6000 fact type apps be doing it?

Is there a better approach instead of creating everything at once? The user may access a view in slot # 400 and begin scrolling from there. Any suggestions are appreciated.

Answer 1

UIViewControllers are lazy. They only load when requested, and automatically unload when memory is tight (and it's easy to unload them manually by calling self.view=nil).

"Load" here means "read a NIB," or "build programmatically." ViewControllers don't really care. Building programmatically can be a little faster since you don't have to hit the disk, but this is seldom the bottleneck, since you only display one view controller at a time.

As to which way to go, it's more style than performance (with the exception of UITableViewCells, which there are reasons you need to build programatically in most cases).

Start by studying the View Controller Programming Guide. It'll show you how iPhone intends you to do this.

To eJames' comment about NIBs being XML files, this may be slightly misleading. NIBs are binary files generated by compiling XIB files which are XML. I'd do actually profiling on the phone before assuming that NIB load time is actually a problem. Much as I am by nature inclined to programatic layout, I've found in practice that NIBs greatly simplify many UI issues in practice, and I always come back to them for large projects.