9.3.1. C++ Class Self Test Answers

Although it's a common practice, and a good starting point, to put data members in a private section and member functions in a public section, we can't assume all members follow this pattern. Instead, it's crucial to check the accessibility symbols at the left of each member and translate them appropriately: "+" translates to a public member and "-" to a private one. Public data are rare, but private "helper" functions are sometimes helpful. You can put all private members in one section and all public members in another. Alternatively, you can create multiple public and private sections, separating data and functions into different groups.

class Car
{
	private:
		string	model;
		int	wheels;
		double	engine_size;

	public:
			Car(string a_name, int a_wheels, double a_engine_size);
		string	get_model();
		bool	is_running();
		void	set_wheels(int w);
		double	accelerate(int fuel_rate);

	public:
		string	vin;

	private:
		int	diagnostics(char system);
};

Version 1: Variables and functions separate. Public member variables are rare, so vin is made public only as a test question. Aside from this invention, the Car class is an authentic example of a simple class. Furthermore, it demonstrates my preferred class organization.

class Car
{
	private:
		string	model;
		int	wheels;
		double	engine_size;
		int	diagnostics(char system);

	public:
			Car(string a_name, int a_wheels, double a_engine_size);
		string	get_model();
		bool	is_running();
		void	set_wheels(int w);
		double	accelerate(int fuel_rate);
		string	vin;
};

Version 2: Private and public members together. Although this class organization is valid, I find mixing the functions and variables makes it more difficult to read.

Unlike Java, the public and private keywords are not applied to the class or individual members. In C++, the keywords label sections of a class: every feature appearing after a label exhibits the labeled accessibility until changed by another label. A class typically has two labeled sections but may have more if needed.

		class ________
		{
			private:
				feature1;
				feature2;
			public:
				feature3;
				feature4;
		};

UML class diagrams do not specify how a function performs its tasks (although other UML diagrams may). So, when we translate UML class diagrams into C++, the translation process only specifies the functions' prototype or signature and does not specify the contents of the functions' bodies.