Call initWithCoder explicitly or ViewDidAppear equivalent in UIView?

Question

In a UIView I have a nav button with an IBAction & method in the top-level view controller.

In the IBAction code, I flip a boolean so that when execution returns to the UIView, there's some new setup prior to drawRect: repainting the view.

If all this were in the ViewController, I could put the new setup code in something like ViewDidAppear so it executes each time the button is pressed. However, there's no such method at the UIView level. There is initWithCoder, but this only seems to be executed once (when the storyboard/nib loads).

So my question is - either, is there a way to call the initiWithCoder method explicitly from my IBAction at the VC level (I've tried [self initWithCoder:nil] but the breakpoint at the UIView level doesn't trigger) or is there a method that runs when execution returns to the UIView level, a la ViewDidAppear?

Thanks

Image of goal:

Answer 1

Unless you really know what you're doing (I mean really know), don't call -initWithCoder: yourself. You're meant to implement it just as you implement -drawRect: and let the system call it. If you ever find yourself calling something like this directly and you can't explain the deep technical reasons why there's no other way, then it's the wrong approach. Read and follow the documentation (not just the method's doc) to make sure you understand whatever method you're using. It'll tell you.

That said, what you're wondering is if there's a point in a view's lifecycle where you can "do something" (check a BOOL and perform some work if YES/NO) any time the view "appears". The answer is yes, and -willMoveToSuperview "can" work.

BUT

That's the "wrong" approach, IMO. The BOOL property ('draw a twiddle next time I'm asked to draw) can and probably should live in the UIView, but its state should be set in its controller since this is specific to your app. Views are supposed to be (highly) reusable; controllers are supposed to implement your app's specific logic and drive the views according to the model state and user (or system) actions.

So: when you want to enable the "draw a twiddle" operation, your view controller should set the view instance's drawTwiddle flag then probably flag the view for drawing. Your view will then have -drawRect: called at some point you shouldn't try to control and, when it does, it sees that self.drawTwiddle == YES and draws the twiddle along with whatever other drawing it does.

At that point, you might be tempted to have the view set its own drawTwiddle flag to NO since the behavior is intended to fire once. Don't do this. BEWARE: Other user actions or system events may call -drawRect: at any time so the twiddle may not actually be seen by the user (it may appear and disappear faster than is visible). 'So', the right thing to do is to make the controller (via some direct action, system event, or timer) responsible for setting and unsetting the drawTwiddle flag, then flagging the view for redisplay.

Adding

It's also unusual to put an IBOutlet or an IBAction in a UIView. Most of the time, unless you're creating some compound control whose parts aren't intended to be accessed and managed individually, your architecture is clearer (and more closely follows the spirit of the MVC design pattern) by letting the controller manage/own the outlets and actions.