<br><br>Hi:<br><br>Through the document in the ol's website,I know that there are so many layers in ol. And Some of them have the inherit chain.<br><br>For example, the <br><br>layer.Layer->layer.HttpRequest->layer.Grid->layer.WMS<br>
<br><br>layer.Grid->layer.TileCache<br> ->layer.WMS<br> ->layer.XYZ<br><br>However, when say inherit,I often think the "polymorphic",But I do not find it in the source codes.<br>
<br>In my opinion,the class who is inherited should own some not-implemented method which will be override by its sub class.<br><br><br>Suppose,the layer.Layer have a method "draw(xxxx)" which is not implementd,then all its sub-class will override this method,when the map need to re-draw,it call the 'draw()' of each layer.<br>
<br>But in ol's source codes,I did not find anything like this.<br><br>So,I wonder what is the inheritance structure in ol?<br>