Processing: Creative Coding and Computational Art

Figure 9-33. Drawing Some Roofs sketch
There is nothing new in this sketch, and I now have all the House component classes built.
The next thing to do is put them all together. Again, it is worthwhile considering this problem
in the context of the real world. If you were really building a house, you would be at
the stage at which you have identified your door, window, and roof suppliers, and have
established an agreed upon set of properties and methods. In a sense, you have developed
a contractual agreement with your suppliers. This is precisely how OOP works.
House class
The public properties and methods of a class are referred to as the public interface to the
class. If you know the public interface to a class, you don’t even need to know what happens
within the class. The interface, in a sense, enforces the contract. Classes should be as
modular and self-contained as possible. Thus, each of the classes takes care of calculating
and drawing itself. The House class is no exception. The House class, besides drawing some
type of external structure, will need to orchestrate how the Door, Window, and Roof component
classes are used in its own creation. To make this happen, you need to somehow
include these classes within the House class. You also want to be able to customize these
component classes. There is a classic OOP way to solve this problem, which is called composition.
I’ll actually include variables of the respective component types within the House
class. In other words, I’ll include reference variables of the Door, Window, and Roof data
types within the House class definition. When I instantiate the House class, I’ll actually pass
in Door, Window, and Roof object references as arguments, which, you’ll remember, will
need to be received by parameters of the same data type within a House constructor.
Here’s the House class. Please note that the following code is not a finished sketch yet, but
only the House class. Shortly, I’ll put all the classes (Window, Door, Roof, and House)
together into a sketch to draw a little neighborhood.
class House{
//house properties
int x;
int y;
int w;
int h;
SHAPES
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