公共示例与受C ++保护的示例

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公开宣布的所有班级成员将向所有人开放。声明为public的数据成员和成员函数也可以由其他类访问。可以使用具有该类对象的直接成员访问运算符(。)从程序中的任何位置访问该类的公共成员。

例子：

// C++ program to demonstrate public
// access modifier
  
#include 
using namespace std;
  
// class definition
class Circle {
public:
    double radius;
  
    double compute_area()
    {
        return 3.14 * radius * radius;
    }
};
  
// main function
int main()
{
    Circle obj;
  
    // accessing public data member outside class
    obj.radius = 5.5;
  
    cout << "Radius is: " << obj.radius << "\n";
    cout << "Area is: " << obj.compute_area();
    return 0;
}

输出：

Radius is: 5.5
Area is: 94.985

在上面的程序中，数据成员的半径是公共的，因此我们可以在类外部访问它。

受保护的

受保护的访问修饰符与私有访问修饰符相似，不同之处在于，声明为“受保护”的类成员在该类外部不可访问，但可以由该类的任何子类(派生类)访问。
例子：

// C++ program to demonstrate
// protected access modifier
#include 
using namespace std;
  
// base class
class Parent {
    // protected data members
protected:
    int id_protected;
};
  
// sub class or derived class
class Child : public Parent {
  
public:
    void setId(int id)
    {
  
        // Child class is able to access the inherited
        // protected data members of base class
  
        id_protected = id;
    }
  
    void displayId()
    {
        cout << "id_protected is: " << id_protected << endl;
    }
};
  
// main function
int main()
{
  
    Child obj1;
  
    // member function of the derived class can
    // access the protected data members of the base class
  
    obj1.setId(81);
    obj1.displayId();
    return 0;
}

公开与受保护之间的区别

Public	Protected
All the class members declared under public will be available to everyone.	Protected access modifier is similar to that of private access modifiers.
The data members and member functions declared public can be accessed by other classes too.	The class member declared as Protected are inaccessible outside the class but they can be accessed by any subclass(derived class) of that class.

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