Getting Started with C + + object-oriented Programming: Classes (Class)

In the last two articles, we emphasize the operation of the knowledge of the structure.

Later, we will gradually complete with C + + as the main body, which means that our tutorials officially into object-oriented programming.

The previous tutorial I have repeatedly explained that the structure of the master is very important, where is the important? Important in the structure and class have the same characteristics, but there is a big difference, the class is the foundation of object-oriented programming, but it is very close to the structure of the relationship.

We create a struct in the C language we use the following methods:

struct test
{
    Private
        int number;
    Public
        float Socre;
};

The class is created in almost the same way as the structure, looking at the following code:

Class Test
{
    Private
        int number;
    Public
        float Socre;
    Public
        int RP ()
        {
            return number;
        }
        void Setnum (int a)
        {
            Number=a;
        }
};

But you notice that no, standard C is not allowed to declare functions in the structure, but C + + class can, this point and C have the essential difference, very good embodiment of C + + object-oriented characteristics!

The past C language is a non object-oriented language

His characteristics are:

program = algorithm + data structure

But the features of C + + are

Object = algorithm + data structure

Program = Object + Object + Object + Object + ...

So according to this feature, we are defining a struct variable of our own definition. This variable should be called an object or an instance.

For example

Test A;

Then A is an object (instance) of the test structure

The members of the test structure body can be called a component, for example:

a.socre=10.1f;

Then number is the component of object A of test structure (called data member, or attribute) score;

Members of a struct in C language their default storage control is public and the default storage control for classes in C + + is private, so members in a class that need to be externally dropped must be added with the keyword Public declaration as a common type, which is also used for member functions in the class. There is not much difference between the operation of a function and the ordinary function.

For example, the RP () member function in the above example, if we have the following definition:

Test A;

, calling RP () should be written as:

A.RP ();

The invocation of a member function is consistent with the invocation of a normal member variable using the. operator.

This section provides a complete example for consolidating contact.

The following (important and special places have detailed annotations):

#include <iostream>
using namespace Std;
Class Test
{
    private://Private member classes cannot be accessed directly
        int number;
    public://Common member classes can be accessed directly
        float Socre;
    Public
        int RP ()
        {
            return number;
        }
        void Setnum (int a)
        {
            Number=a;
        }
};
void Main ()
{
    Test A;
    a.number=10;//wrong, private member cannot access external
    a.socre=99.9f;
    cout<<a.socre<<endl;//Public members can be accessed externally
    A.setnum (100)//The assignment of private member number indirectly via public member function Setnum ()
    COUT<<A.RP ()//indirect Returns the value of private member number
    Cin.get ();
}

OK, here's how to define a member function (method) inside a class, and let's look at the domain specifier (::).