The Composite pattern
“I really liked the way you used the Composite pattern with your bicycle models. You were able to leverage the pattern to compute component cost and weight for shipping. But you modeled a special structure just for that purpose,” said Tom.
Kitty fielded the criticism, saying, “A separate structure met our needs at the time we built it. We already had our classes in production code and we didn’t want to violate the open-closed principle of SOLID.” We covered SOLID in Chapter 2.
Tom wanted to build a Composite pattern directly into the structure of the wheelchair. This was a little bit challenging because he didn’t necessarily want the structural requirements of the composite to define the structure of the wheelchair. Instead, what he really needed was a normal object structure that acted as a composite. “We can improve on your design by baking the composite structure directly into all our objects. We need...
