我真的需要自定义UIView中的drawRect（）吗？

Question

I am new to iOS and trying to understand the use for drawRect() in custom UIViews, so I have simple custom view which I initialize from code.I want to update its colors for instance and I see two approaches as shown below. Which one should I use and why?

//VController
CustomView *cv = [[CustomView alloc] initWithFrame:...]
...
[cv updateColors];

//CustomView
-(id) initWithFrame {}
-(id) initWithCoder  {}
-(void) updateColors(UIColor *color){  ----(1)
  ...Draw here with new color ...
   view1.backgroundColor = color;
   view2.backgroundColor = color;

 }
- (void) drawRect{
 ... draw here with new color ... ---------(2)
   view1.backgroundColor = color;
   view2.backgroundColor = color;
 }

Answer 1

If all you want to do is change the background color of this view or some of its subviews, you absolutely should not misuse drawRect: for this. drawRect: is for when you want to draw the view (ie its content) when the system believes its needs refreshing; it is called at many and unpredictable times, and you don't need that - you just need to change the background color, a feature of the view, on demand. Similarly drawRect: is not the place to perform management of subviews.

But if you are going to draw the view's content (eg the view displays a circle and you need to draw that circle to portray the view) then you must use drawRect: for that; it is the only place where the view gets a chance to draw itself.