layoutSubviews Considered Reentrant

I had the weirdest bug the other day: rotating the iPhone worked fine in iOS 7, but not in iOS 8. Actually it was weirder: Some UIView instances adjusted themselves perfectly after the rotation, but some had the wrong size (even though they all had the exact same UIView subclass).

After some digging I discovered that layoutSubview was called several times during rotation, and each time the view had a different frame. Moreover, these calls were not happening sequentially! Instead, layoutSubviews was called with frame1, and before returning it was being called with frame2, and before returning form that it was called with frame3 — all for the same UIView.

There wasn’t a lot of code in my layoutSubviews, nothing that takes long. But it was apparently long enough to cause a bug in some instances.

My solution was to schedule a layout update for a split second later:

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