9.4 const and static Members

Statements for constants

#define VALUE 100
const int value = 100;
const int * p_int;
int const * p_int;
int * const p_int;
void func(const int *);
void func(const int &);

const member variables behavior similar with normal const variables
const member functions promise not to modify member variables.

class Student
{
  private:
    const int BMI = 24;
    // ...
  public:
    Student()
    {
        BMI = 25; //can it be modified? no
        // ...
    }
    int getBorn() const
    {
        born++; //Can it be modified?
        return born;
    }
};

static members
static members are not bound to class instances
静态成员是不绑定到某一个实例的

class Student
{
  private:
    static size_t student_total; // declaration only
  public:
    Student()
    {
        student_total++;
    }
    ~Student()
    {
        student_total--;
    }
    static size_t getTotal() {return student_total;}
};
// definition it here
size_t Student::student_total = 0;