cpp - define Class－KwCheng's blog

In C++, classes are very much like structs, except that classes provide much more power and flexibility.

In C++, when we declare a variable of a class, we call it instantiating the class. The variable itself is called an instance of the class. A variable of a class type is also called an object.

In addition to holding data, classes can also contain functions! Here is our Date class with a function to set the date:

class Date

{

public:

int m_nMonth;

int m_nDay;

int m_nYear;

void SetDate(int nMonth, int nDay, int nYear)

{

m_nMonth = nMonth;

m_nDay = nDay;

m_nYear = nYear;

}

};

The function is called inline function because it is decined in the class.

We can also define the body of function outside the class as follow :

class Date
{
public:
    int m_nMonth;
    int m_nDay;
    int m_nYear;
       void SetDate(int nMonth, int nDay, int nYear);
};

void Date::SetDate(int nMonth, int nDay, int nYear)
{
    m_nMonth = nMonth;
    m_nDay = nDay;
    m_nYear = nYear;
}