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C語(yǔ)言

C++ 的三種訪問(wèn)權(quán)限與三種繼承方式

時(shí)間:2024-12-27 21:14:16 C語(yǔ)言 我要投稿
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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;

  };


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