Design Patterns Explained

Chapter 12 • Solving the CAD/CAM Problem with Patterns 211
Figure 12-1O After applying the Bridge and Facade patterns.
Applying the Facade pattern means that I insert a facade between
the V1 modules and the VlImp object that is going to use them.
v1Facade has simplified methods that relate to what Vlimp needs
to do. Each method in ViFacade will look like a series of function
calls on the V1 system.
The kind of information that I need in order to call these functions
will determine how v1Imp is implemented. For example, when
using V1, I need to tell it which model to use and what the Feature's
ID is. All Vlimp objects that use the ViFacade will therefore need to
know this information. Since this is implementation-specific
information, it will need to know it itself, rather than getting it from
the calling Feature. Thus, in a V1 system, each Feature will need
its own Vlimp object (to remember system-specific information
about the feature). I will go over this in more detail once the general
architecture is completed.
The Facade