1. Global variable
This is the least desire way, though it is probably the easiest way. However, this way is most difficult to
maintain. With this, it is almost impossible to know which UIViews are related. When changes make to
one, it is also very difficult to assess which other will be impacted.
2. Message passing
Public variable can be setup in the UIViews. Setter method can be automatically generated by using the
@synchronize keyword. The setter method can be invoke to pass the message.
Setup delegate interface in the UIView that will be call when there are event changes in the calling