CODEWITHSUNDEEP
iosobjective-cuiviewdrawrect
paulmrest
paulmrest

Reputation: 412

Single drawRect implementation across multiple UIView subclasses

Across my app I have several different subclasses of UIView: UIDatePicker, UIPicker, UIButton, UITableView, UITableViewCell, UITextView, etc. etc... For each of these I'd like to add a very simple drawRect custom implementation that I have working great.

Is there a simple way to get multiple subclasses of UIView to all have the same drawRect implementation without creating a subclass and repeating the same code across each UIPicker, UIButton, etc. etc... ?

I realize the solution to this is probably to write a delegate class for UIView's layer property and do the custom drawing in drawLayer, but I thought I would ask before I go re-working my code.

Upvotes: 2

Views: 230

Answers (1)

paulmrest
paulmrest

Reputation: 412

The answer seems to be no.

Furthermore, it appears that my idea for the workaround also doesn't work: I was thinking I could write a nice little class that implements the drawLayer method from CALayerDelegate and do the drawing in there, and then in each UIView or UIView subclass' init method do a self.layer.delegate = niceLittleCALayerDelegateClass.

My research, however, happened upon this: https://developer.apple.com/library/ios/documentation/GraphicsImaging/Reference/CALayer_class/#//apple_ref/occ/instp/CALayer/delegate which contains the damning sentence: In iOS, if the layer is associated with a UIView object, this property must be set to the view that owns the layer.

So, double nope.

Against rmaddy's advice I'm going to just write a subclass for each of the UIView subclasses I want to implement this drawing behavior in. We'll see how that goes.

Update:

I can't believe I didn't think of this before, but the "right" way to do this (that is to say without subclassing UIView's subclasses and adding a custom drawRect method to each subclass's subclass), from everything I can find, seems to be to either create a subview or a sublayer with a transparent background that does whatever custom drawing you want.

Obviously this is going to draw on top of the UIView you're actually using, so this would get exceedingly complicated if you're trying to draw things that interact with the default elements of the UIView, but for my purposes (just a simple frame drawn with a UIBezierPath) it seems to work great.

At present I'm not sure if the subview or the sublayer approach is more efficient. If anyone can shed light on that, I'd appreciate it.

Upvotes: 2

Related Questions