Design Patterns Explained

212 Part IV • Putting It All Together: Thinking in Patterns
Pick Adapter next
Taking advantage of nongeneralities to debug code.
Earlier in this chapter, I mentioned that some of the methods of
the implementation should only be called by certain Feature
objects. I can take advantage of knowing what should be calling
what to put checks in the code. I do not need to do this, and I
may need to remove these checks if the rules change. Nevertheless,
it can be useful the first time in.
For example, in the CAD/CAM solution, there are Features
containing an implementation object. One of the implementation
methods is getEdgeType. This only makes sense if a Feature is a
slot or a cutout. Other Features do not have edge types. If I have
implemented things properly, the getEdgeType method will
never get called except by slots and cutouts. I can check that this
happens by using an assert in the getEdgeType method that
verifies that the calling Feature is of the appropriate type.
Thinking in Patterns: Step 2d (Adapter)
Having applied Facade, I can now apply Adapter. This results in
Figure 12-11.
Figure 12-11 After applying the Bridge, Facade, and Adapter.