Some controls have internal subviews you’d want to modify, but you cannot control the class that’s used internally. This example shows extending just that singleton (the view instance) by defining the method inline. This is preferable to using ‘categories’, because those affect _all_ instances of that class.

zomg.rb

def presentAlert
  alert = UIAlertView.new
  # ...

  textField = alert.textFieldAtIndex(0)
  # *Only for this UITextField instance*, move the leftView 4 points to the right.
  def textField.leftViewRectForBounds(bounds)
    CGRectOffset(super, 4, 0)
  end

  alert.show
end