C++ 的三種訪問權限與三種繼承方式
我們知道C++中的類，有三種訪問權限(也稱作訪問控制)，它們分別是public、protected、private。要理解它們其實也很容易，以下是為大家分享的C++ 的三種訪問權限與三種繼承方式，供大家參考借鑒，歡迎瀏覽!
父類：
class Person
{
public:
Person(const string& name, int age) : m_name(name), m_age(age)
{
}
void ShowInfo()
{
cout << "姓名：" << m_name << endl;
cout << "年齡：" << m_age << endl;
}
protected:
string m_name; /pic/p>
private:
int m_age; /pic/p>
};
class Person
{
public:
Person(const string& name, int age) : m_name(name), m_age(age)
{
}
void ShowInfo()
{
cout << "姓名：" << m_name << endl;
cout << "年齡：" << m_age << endl;
}
protected:
string m_name; /pic/p>
private:
int m_age; /pic/p>
};
子類：
class Teacher : public Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "姓名：" << m_name << endl; /pic/p>
cout << "年齡：" << m_age << endl; /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
class Teacher : public Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "姓名：" << m_name << endl; /pic/p>
cout << "年齡：" << m_age << endl; /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
調用方法：
void test()
{
Person person("張三", 22);
person.ShowInfo(); /pic/p>
cout << person.m_name << endl; /pic/p>
cout << person.m_age << endl; /pic/p>
}
void test()
{
Person person("張三", 22);
person.ShowInfo(); /pic/p>
cout << person.m_name << endl; /pic/p>
cout << person.m_age << endl; /pic/p>
}
總結
我們對C++類三種方式控制權限總結如下，這與Java中的三種對應的訪問權限是一樣的。
qq%e6%88%aa%e5%9b%be20161104113813
三種繼承方式
C++中繼承的方式還有多種，也分別都用public、protected、private表示。這與Java不一樣，Java只有繼承的概念，默認是public繼承的。
1. 三種繼承方式不影響子類對父類的訪問權限，子類對父類只看父類的訪問控制權。
如下面三種繼承方式都能訪問父類中的public和protected成員。
class Teacher : /*public*/ /*protected*/ private Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "姓名：" << m_name << endl; /pic/p>
/pic/pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
class Teacher : /*public*/ /*protected*/ private Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "姓名：" << m_name << endl; /pic/p>
/pic/pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
2. 繼承方式是為了控制子類(也稱派生類)的調用方(也叫用戶)對父類(也稱基類)的訪問權限。
public繼承
class Teacher : public Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
class Teacher : public Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
void TestPublic()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo();
cout << endl;
teacher.ShowTeacherInfo();
}
void TestPublic()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo();
cout << endl;
teacher.ShowTeacherInfo();
}
結果：
姓名：李四
年齡：35
姓名：李四
年齡：35
職稱：副教授
private繼承：
class Teacher : private Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
class Teacher : private Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
void TestPrivate()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); /pic/p>
cout << endl;
teacher.ShowTeacherInfo();
}
void TestPrivate()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); /pic/p>
cout << endl;
teacher.ShowTeacherInfo();
}
3. public、protected、private三種繼承方式，相當于把父類的public訪問權限在子類中變成了對應的權限。
如protected繼承，把父類中的public成員在本類中變成了protected的訪問控制權限；private繼承，把父類的public成員和protected成員在本類中變成了private訪問控制權。
protected繼承：
class Teacher : protected Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
class Teacher : protected Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); /pic/p>
cout << "職稱：" << m_title << endl; /pic/p>
}
private:
string m_title; /pic/p>
};
void TestProtected()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); /pic/p>
cout << endl;
teacher.ShowTeacherInfo();
}
void TestProtected()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); /pic/p>
cout << endl;
teacher.ShowTeacherInfo();
}
class Leader : public Teacher
{
public:
Leader(const string& name, int age, const string& title, string position)
: Teacher(name, age, title), m_position(position)
{
}
void ShowLeaderInfo()
{
ShowInfo(); /pic/p>
ShowTeacherInfo(); /pic/p>
cout << m_position << endl;
}
private:
string m_position;
};
class Leader : public Teacher
{
public:
Leader(const string& name, int age, const string& title, string position)
: Teacher(name, age, title), m_position(position)
{
}
void ShowLeaderInfo()
{
ShowInfo(); /pic/p>
ShowTeacherInfo(); /pic/p>
cout << m_position << endl;
}
private:
string m_position;
};
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