Thinking in C++ Introduction to Objects

Thinking in C++, Cours C/C++, tutoriel & guide de travaux pratiques en pdf.

How will we build it?

In this phase you must come up with a design that describes what the classes look like and how they will interact. An excellent technique in determining classes and interactions is the ClassResponsibility-Collaboration (CRC) card. Part of the value of this tool 10 My personal take on this has changed lately. Doubling and adding 10 percent will give you a reasonably accurate estimate (assuming there are not too many wild-card factors), but you still have to work quite diligently to finish in that time. If you want time to really make it elegant and to enjoy yourself in the process, the correct multiplier is more like three or four times, I believe.

Introduction to Objects

is that it’s so low-tech: you start out with a set of blank 3” by 5” cards, and you write on them. Each card represents a single class, and on the card you write :

1. The name of the class. It’s important that this name capture the essence of what the class does, so that it makes sense at a glance.

2. The “responsibilities” of the class: what it should do. This can typically be summarized by just stating the names of the member functions (since those names should be descriptive in a good design), but it does not preclude other notes. If you need to seed the process, look at the problem from a lazy programmer’s standpoint: What objects would you like to magically appear to solve your problem?

3. The “collaborations” of the class: what other classes does it interact with? “Interact” is an intentionally broad term; it could mean aggregation or simply that some other object exists that will perform services for an object of the class. Collaborations should also consider the audience for this class. For example, if you create a class Firecracker, who is going to observe it, a Chemist or a Spectator? The former will want to know what chemicals go into the construction, and the latter will respond to the colors and shapes released when it explodes. You may feel like the cards should be bigger because of all the information you’d like to get on them, but they are intentionally small, not only to keep your classes small but also to keep you from getting into too much detail too early. If you can’t fit all you need to know about a class on a small card, the class is too complex (either you’re getting too detailed, or you should create more than one class). The ideal class should be understood at a glance. The idea of CRC cards is to assist you in coming up with a first cut of the design so that you can get the big picture and then refine your design.