swift: Is correct to use stored properties as computed properties

Question

I'm try to achieve this objective-c code

@property (strong) UIView *customView;

-(UIView*)customView
{
   if (!customView){
       self.customView = [[UIView alloc]init];
       self.customView.backgroundColor = [UIColor blueColor];
  }
   return customView;
}

Why am I use this? customView called from many place, so we have to check this condition in all place. To avoid this duplication, I wrote this.

So I'm try to create stored properties and also use getter method to check if already either created or not.

var mainView : UIView? {

  get{
   if let customView = self.mainView{
        return self.mainView
   }
   var customView : UIView = UIView() 
   self.mainView = customView
   self.mainView.backgroundColor = UIColor(blueColor)
   return customView 
 }
 set{
  self.mainView = newValue
  }
}

Is this correct? or any other approach to do this?

Note: There's no warning or error with above code. But confusion with stored and computed properties. Please make me clear.

Answer 1

Not sure why, but lazy variables combined with computed properties result in an error:

'lazy' attribute may not be used on a computed property

But this seems to work:

class MyClass {
  @lazy var customView: NSView = {
    let view = NSView()
    // customize view
    return view
  }()
}