The OpenLayers.Layer class

So far, we've only been using the OpenLayers.Layer.WMS class in the examples. This has been the beginning of all our layer object instantiation code so far:

var wms = new OpenLayers.Layer.WMS(

Notice the period between Layer and WMS: Layer.WMS. This means that we're accessing the WMS subclass of the Layer superclass. What do I mean when I say this? Well, the WMS class is a subclass of the Layer class, so let's briefly refresh our knowledge about subclasses.

Subclasses

In Chapter 1, we mentioned Subclasses. Subclasses are, basically, classes that derive from some base class. This base class is called a Superclass. The Layer class is thus the Superclass of all Layer subclasses (Superclasses and Subclasses are still classes). Subclasses inherit all the properties of their superclass.

Layer Class—Sub and super classes

The Layer class is therefore the superclass from which all other Layer classes derive. The Layer.WMS layer class is different from the Layer.Image class, and...