- 相關(guān)推薦
C++ 的三種訪問(wèn)權(quán)限與三種繼承方式
我們知道C++中的類,有三種訪問(wèn)權(quán)限(也稱作訪問(wèn)控制),它們分別是public、protected、private。要理解它們其實(shí)也很容易,以下是為大家分享的C++ 的三種訪問(wèn)權(quán)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; //姓名
private:
int m_age; //年齡
};
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; //姓名
private:
int m_age; //年齡
};
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(); //正確,public屬性子類可見(jiàn)
cout << "姓名:" << m_name << endl; //正確,protected屬性子類可見(jiàn)
cout << "年齡:" << m_age << endl; //錯(cuò)誤,private屬性子類不可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
class Teacher : public Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); //正確,public屬性子類可見(jiàn)
cout << "姓名:" << m_name << endl; //正確,protected屬性子類可見(jiàn)
cout << "年齡:" << m_age << endl; //錯(cuò)誤,private屬性子類不可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
調(diào)用方法:
void test()
{
Person person("張三", 22);
person.ShowInfo(); //public屬性,對(duì)外部可見(jiàn)
cout << person.m_name << endl; //protected屬性,對(duì)外部不可見(jiàn)
cout << person.m_age << endl; //private屬性,對(duì)外部不可見(jiàn)
}
void test()
{
Person person("張三", 22);
person.ShowInfo(); //public屬性,對(duì)外部可見(jiàn)
cout << person.m_name << endl; //protected屬性,對(duì)外部不可見(jiàn)
cout << person.m_age << endl; //private屬性,對(duì)外部不可見(jiàn)
}
總結(jié)
我們對(duì)C++類三種方式控制權(quán)限總結(jié)如下,這與Java中的三種對(duì)應(yīng)的訪問(wèn)權(quán)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(rèn)是public繼承的。
1. 三種繼承方式不影響子類對(duì)父類的訪問(wèn)權(quán)限,子類對(duì)父類只看父類的訪問(wèn)控制權(quán)。
如下面三種繼承方式都能訪問(wèn)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(); //正確,public屬性子類可見(jiàn)
cout << "姓名:" << m_name << endl; //正確,protected屬性子類可見(jiàn)
//cout << "年齡:" << m_age << endl; //錯(cuò)誤,private屬性子類不可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
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(); //正確,public屬性子類可見(jiàn)
cout << "姓名:" << m_name << endl; //正確,protected屬性子類可見(jiàn)
//cout << "年齡:" << m_age << endl; //錯(cuò)誤,private屬性子類不可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
2. 繼承方式是為了控制子類(也稱派生類)的調(diào)用方(也叫用戶)對(duì)父類(也稱基類)的訪問(wèn)權(quán)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(); //正確,public屬性子類可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
class Teacher : public Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); //正確,public屬性子類可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
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(jié)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(); //正確,public屬性子類可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
class Teacher : private Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); //正確,public屬性子類可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
void TestPrivate()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); //錯(cuò)誤,因?yàn)門eacher采用了private的繼承方式,外部不可訪問(wèn)。
cout << endl;
teacher.ShowTeacherInfo();
}
void TestPrivate()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); //錯(cuò)誤,因?yàn)門eacher采用了private的繼承方式,外部不可訪問(wèn)。
cout << endl;
teacher.ShowTeacherInfo();
}
3. public、protected、private三種繼承方式,相當(dāng)于把父類的public訪問(wèn)權(quán)限在子類中變成了對(duì)應(yīng)的權(quán)限。
如protected繼承,把父類中的public成員在本類中變成了protected的訪問(wèn)控制權(quán)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(wèn)控制權(quán)。
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(); //正確,public屬性子類可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
class Teacher : protected Person
{
public:
Teacher(const string& name, int age, const string& title)
: Person(name, age), m_title(title)
{
}
void ShowTeacherInfo()
{
ShowInfo(); //正確,public屬性子類可見(jiàn)
cout << "職稱:" << m_title << endl; //正確,本類中可見(jiàn)自己的所有成員
}
private:
string m_title; //職稱
};
void TestProtected()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); //錯(cuò)誤,基類Person的ShowInfo此時(shí)對(duì)Teacher相當(dāng)于protected的,外部不可以被訪問(wèn)
cout << endl;
teacher.ShowTeacherInfo();
}
void TestProtected()
{
Teacher teacher("李四", 35, "副教授");
teacher.ShowInfo(); //錯(cuò)誤,基類Person的ShowInfo此時(shí)對(duì)Teacher相當(dāng)于protected的,外部不可以被訪問(wèn)
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(); //基類Person的ShowInfo此時(shí)相當(dāng)于protected的,但子類仍可以訪問(wèn)
ShowTeacherInfo(); //ShowTeacherInfo仍然是public的,可以訪問(wèn)
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(); //基類Person的ShowInfo此時(shí)相當(dāng)于protected的,但子類仍可以訪問(wèn)
ShowTeacherInfo(); //ShowTeacherInfo仍然是public的,可以訪問(wèn)
cout << m_position << endl;
}
private:
string m_position;
};
【C++ 的三種訪問(wèn)權(quán)限與三種繼承方式】相關(guān)文章:
C語(yǔ)言訪問(wèn)MCU寄存器的三種方式06-08
php遞歸函數(shù)三種方式02-21
Java編程里的包及訪問(wèn)權(quán)限08-14
關(guān)于C++中定義比較函數(shù)的三種方法05-30
路由器連接電腦的三種方式02-18