http://www.runoob.com/cplusplus/cpp-data-encapsulation.html
1 simple example
class Box
{
public:
double getVolume(void)
{
return length * breadth * height;
}
private:
double length; // 长度
double breadth; // 宽度
double height; // 高度
};
Examples of encapsulated data
C ++ program, any class with public and private member can be used as examples of data abstraction and encapsulation data. Consider the following examples:
#include <the iostream>
the using namespace STD;
class the Adder {
public:
// Constructor
the Adder (int I = 0)
{
Total = I;
}
// external interface
void addNum (int Number)
{
Total + = Number;
}
/ / external interface
int getTotal ()
{
return Total;
};
Private:
// hide the external data
int Total;
};
int main ()
{
the Adder a;
a.addNum (10);
a.addNum (20 is);
a .addNum (30);
cout << "Total " << a.getTotal() <<endl;
return 0;
}
2C ++ object-oriented programming Introduction
Data encapsulation is a mechanism to function data and operation data bundled together, data abstraction is an interface to a user and is exposed only to hide the implementation details of the mechanism.
Object-oriented programming (Object Oriented Programming), referred to OOP.
In the conventional process-oriented programming, data and related data manipulation functions are separate independent entity;
Objects, such objects are in fact all around; for programming perspective, the object comprising A) a series of attributes (data); B) a series of operations (functions).
OOP object provides design features, properties and behavior of an object comprising, include both together, constitute the object entity (i.e. an entity class);
Object entity, make the program more modular, easier to read and easy to write, improved code reuse to a higher level;
Object provides a direct method for data manipulation, defines the interaction, and the interaction between the object and how the object;
More importantly, OOP provides a more practical concepts: encapsulation, inheritance, polymorphism and abstraction.
This focuses on the package, i.e., the encapsulated data object to a class and operation function entity.
One essential difference between the structure and the class is a member of the class identifier may be used to control their accessibility;
Typically, the member variable classes, a prefix 'm_' to distinguish:
3 Constructor Ⅰ
1) Constructor: is a special member function is performed when the class is instantiated; normally to initialize member variables.
Constructor clear naming rules: A) the function names and class names must be the same; B) no return type (including void).
No argument constructor - constructor with no arguments, the default constructor for the class:
Typically, the class contains a default constructor, you can initialize member variables.
Containing argument constructor - Constructor a parameter, the specified value can be imparted to the member variables;
Two or more constructors, similar overloaded functions; constructors must have a unique front (the number of parameters and parameter types).
Class can also contain only argument constructor, no default constructor:
4 destructor
析构函数是类的另一种特殊的函数，当类的对象销毁时调用；它和构造函数是成对出现的。
普通的简单类，一般不需要析构函数；因为C++会自动回收垃圾；
如果类中执行了某些动态内存分配，则需要显式定义析构函数，并释放回收垃圾；
析构函数的明确命名规则：A)函数名和类名一样，并前缀'~'；B)不能带参数（即意味着只有一个析构函数）；C)没有返回类型。
注意动态分配，必须提供析构函数，来回收分配的空间。
5 静态成员函数
不用创建即可以访问
如静态成员变量一样，静态成员函数是属于类的本身，不属于任何类的对象；
如静态成员变量访问一样，可以通过：类名::静态成员来访问类的静态成员变量。
注意：静态成员函数，没有this指针；
例如：
6 类代码和头文件
头文件的使用可达到重用的效果；所以将类的定义放在头文件中，而成员函数放在.cpp中定义；而cpp的名字需和类的名字相同。
Date.h:
Date.cpp:
推荐分离类的定义中的成员函数到类外定义。