Design Patterns Explained

Chapter 12 • Solving the CAD/CAM Problem with Patterns 2O3
Start with (and
When I am considering which pattern creates context for the others, I
reject) Abstract
begin with Abstract Factory. The Abstract Factory's context is
Factory
determined by the objects it needs to instantiate, as shown by the
following:
• There will be a set of make methods, the implementation of
each having a return new xxx in it.
• At this time, I do not know what xxx will be.
• xxx will be determined by the objects I am using.
• The objects that I will need to use are defined by other patterns.
Since I cannot even define the Abstract Factory until I know the
classes the other patterns will define, it is not the seniormost pattern
(the pattern that creates the context for the other patterns).
Therefore, I reject it for now as the pattern to start working on.
In fact, the Abstract Factory will be the last pattern I do (unless
another creational pattern shows up during my initial design, in
which case, both creational patterns will vie for being last).
Seniormost patterns constrain the other patterns.
Seniormost is my term for the one or two patterns that establish a
context for the other patterns in my system. This is the pattern
that constrains what the other patterns can do. Other terms you
could use are outermost patterns or context-setting patterns.
There are three pairs of patterns left to consider: Three pairs left
• Adapter-Bridge
• Bridge-Facade
• Facade-Adapter