Assembling Views and Animations(Chapter 6 of The iPhone™ Developer’s Cookbook)

　　Views store arrays of their children. Retrieve this array by calling [aView subviews]. Onscreen, the child views are always drawn after the parent, in the order that they appear in the subviews array.These views draw in order from back to front, and the subviews array mirrors that drawing pattern.Views that appear later in the array are drawn after views that appear earlier.