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C++ 继承 派生类的拷贝构造

作者：我家小花儿 | 2024-08-10 05:01:15

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C++ 继承 派生类的拷贝构造

继承

派生类的拷贝构造

拷贝构造，也是一种构造函数，也没有被继承下来。

语法:

派生类::派生类(const 派生类& another):基类(another),派生类新成员(another.新成员)
{
    //派生类新成员(another.新成员)
}

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构造顺序

在这里插入图片描述

父类中，一部分成员需要拷贝构造来完成，

子类中，也有一部成员需要拷贝构造来完成。

子类中的内嵌子对象也需要拷贝构造来完成

拷贝构造

引例1: 当子类,不自实现拷贝构造时,默认调用父类的拷贝构造

#include <iostream>
using namespace std;


//当子类,不自实现拷贝构造时,默认调用父类的拷贝构造
class A{
    public:
        A(){
            cout << " A ()" << endl;
        }
        A(const A& other){
            cout << " A (const A& other)" << endl;
        }

};

class B: public A{
public:
    B(){
        cout << " B ()" << endl;
    }

    int b;
};

int main() {

    B b;
    B bb(b);
    
    return 0;
}

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输出:
 A ()
 B ()
 A (const A& other)

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引例2: 子类自实现拷贝构造,不做特殊处理时,只会调用父类的构造器.

#include <iostream>
using namespace std;

//子类自实现拷贝构造,不做特殊处理时,只会调用父类的构造器.
class A{
    public:
        A(){
            cout << " A ()" << endl;
        }
        A(const A& other){
            cout << " A (const A& other)" << endl;
        }

};

class B: public A{
public:
    B(){
        cout << " B ()" << endl;
    }
    B(const B& other){
        cout << " B (const A& other)" << endl;
    }


    int b;
};


int main() {

    B b;
    B bb(b);
    
    return 0;
}

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输出:
 A ()
 B ()
 A ()
 B (const A& other)

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引例3: 显示的调用父类的拷贝构造器。

#include <iostream>
using namespace std;


//当子类,不自实现拷贝构造时,默认调用父类的拷贝构造
//子类自实现拷贝构造,不做特殊处理时,只会调用父类的构造器.
class A{
    public:
        A(int x){
            a=x;
            cout << " A ()" << endl;
        }
        A(const A& other){
            a=other.a;
            cout << " A (const A& other)" << endl;
        }
        int a;
};

class B: public A{
public:
    B(int x,int b):A(x){
        this->b=b;
        cout << " B ()" << endl;
    }
    
    //显示的调用父类的拷贝构造器。     //子类对象赋值给父类引用,赋值兼容
    B(const B& other):A(other){
        b=other.b;
        cout << " B (const A& other)" << endl;
    }


    int b;
};


int main() {
    B b(200,100);
    B bb(b);
    cout<<b.a<<endl;
    cout<<b.b<<endl;
    return 0;
}

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案例:

# include <iostream>
using namespace std;

class Birthday{
private:
    int year_;
    int month_;
    int day_;


public:
    Birthday(int year=0, int month=0, int day=0): year_(year), month_(month), day_(day){}
    void Birthdayprint(){
        cout <<"Birthday:"<< year_ << "/" << month_ << "/" << day_ << endl;
    }

};

class Student{
private:
    Birthday birthday_;
    string name_;
    char sex_;
    float score_;

public:
    Student(string name, char sex, float score , int year, int month, int day): name_(name), sex_(sex), score_(score),birthday_(year, month, day){}
    Student(const Student& other){
        cout<<" Student (const Student& other)"<<endl;
        this->name_ = other.name_;
        this->sex_ = other.sex_;
        this->score_ = other.score_;
    }

    void print(){
        cout << "Name: " << name_ << endl;
        cout << "Sex: " << sex_ << endl;
        cout << "Score: " << score_ << endl;
        birthday_.Birthdayprint();
    }
};


class Graduate: public Student{
private:
    float salary_;

public:
    Graduate(string name, char sex, float score, float salary, int year, int month, int day): Student(name, sex, score, year, month, day), salary_(salary){}

    Graduate(const Graduate& other):Student(other){
        cout<<" Graduate (const Graduate& other)"<<endl;
        this->salary_ = other.salary_;
    }
    void pri(){
        print();
        cout << "Salary: " << salary_ << endl;
    }
};

class Doctor: public Graduate{
private:
    string title_;
public:
    Doctor(string name, char sex, float score, float salary, int year, int month, int day, string title): Graduate(name, sex, score, salary, year, month, day), title_(title){}
    Doctor(const Doctor& other):Graduate(other){
        cout << " Doctor (const Doctor& other)" << endl;
        this->title_ = other.title_;
    }


    void Dpri(){
        pri();
        cout << "Title: " << title_ << endl;
    }
};


int main(){

    Graduate g("Alice", 'F', 95.5, 5000 , 2000, 1, 1);
    g.pri();
    cout <<"==============="<< endl;
    Doctor d("Bob", 'M', 85.0, 4000, 2000, 1, 1, "Doctor");
    d.Dpri();

    cout <<"==============="<< endl;


    Doctor d2(d);
    d2.Dpri();

    return 0;
}



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内嵌函数的拷贝构造

引例1 :当内嵌子对象,子类不自实现拷贝构造时,默认调用内嵌子对象的拷贝构造

#include <iostream>
using namespace std;
//todo 内嵌子对象

class C{
public:
    
    C(){
        cout << " C ()" << endl;
    }
    C(const C& other){
        cout << " C (const C& another)" << endl;
    }

};

class A{
public:
    A(int x){
        a=x;
        cout << " A ()" << endl;
    }

    A(const A& other){
        a=other.a;
        cout << " A (const A& other)" << endl;
    }
    int a;
};

class B: public A{
public:
    B(int x,int b):A(x){
        this->b=b;
        cout << " B ()" << endl;
    }
    //当内嵌子对象,子类不自实现拷贝构造时,默认调用内嵌子对象的拷贝构造
    int b;
    C c;
};


int main() {

    B b(200,100);
    B bb(b);


    return 0;
}

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输出:
A ()
 C ()
 B ()
 A (const A& other)
 C (const C& another)

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引例2: 子类自实现的拷贝构造,不做特殊处理,此时只会调用内嵌对象的构造器,此时失去了内嵌对象的拷贝构造的意义


#include <iostream>
using namespace std;
//todo 内嵌子对象

class C{
public:
    C(){
        cout << " C ()" << endl;
    }
    C(const C& other){
        cout << " C (const C& another)" << endl;
    }

};

class A{
public:
    A(int x){
        a=x;
        cout << " A ()" << endl;
    }

    A(const A& other){
        a=other.a;
        cout << " A (const A& other)" << endl;
    }
    int a;
};

class B: public A{
public:
    B(int x,int b):A(x){
        this->b=b;
        cout << " B ()" << endl;
    }
    //子类自实现的拷贝构造,不做特殊处理,此时只会调用内嵌对象的构造器,此时失去了内嵌对象的拷贝构造的意义
    B(const B& other):A(other){
        b=other.b;
        cout << " B (const A& other)" << endl;
    }


    int b;
    C c;
};


int main() {

    B b(200,100);
    B bb(b);


    return 0;
}



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输出:
 A ()
 C ()
 B ()
 A (const A& other)
 C ()
 B (const A& other)

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引例3: 显示的调用内嵌对象的拷贝构造器


#include <iostream>
using namespace std;
//todo 内嵌子对象

class C{
public:
    //当内嵌子对象,
    C(){
        cout << " C ()" << endl;
    }
    C(const C& other){
        cout << " C (const C& another)" << endl;
    }

};

class A{
public:
    A(int x){
        a=x;
        cout << " A ()" << endl;
    }

    A(const A& other){
        a=other.a;
        cout << " A (const A& other)" << endl;
    }
    int a;
};

class B: public A{
public:
    B(int x,int b):A(x){
        this->b=b;
        cout << " B ()" << endl;
    }
    //显示调用内嵌子对象的拷贝构造
    B(const B& other):A(other),c(other.c){
        b=other.b;
        cout << " B (const A& other)" << endl;
    }
    int b;
    C c;
};


int main() {

    B b(200,100);
    B bb(b);
    return 0;
}


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输出:
 A ()
 C ()
 B ()
 A (const A& other)
 C (const C& another)
 B (const A& other)

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案例:

# include <iostream>
using namespace std;

class Birthday{
private:
    int year_;
    int month_;
    int day_;


public:
    Birthday(int year=0, int month=0, int day=0): year_(year), month_(month), day_(day){}
    Birthday(const Birthday& other){
        cout<<" Birthday (const Birthday& other)"<<endl;
        this->year_ = other.year_;
        this->month_ = other.month_;
        this->day_ = other.day_;
    }
    void Birthdayprint(){
        cout <<"Birthday:"<< year_ << "/" << month_ << "/" << day_ << endl;
    }
};

class Student{
private:

    string name_;
    char sex_;
    float score_;
    Birthday birthday_;
public:
    Student(string name, char sex, float score , int year, int month, int day): name_(name), sex_(sex), score_(score),birthday_(year, month, day){}
    Student(const Student& other):birthday_(other.birthday_){
        cout<<" Student (const Student& other)"<<endl;
        this->name_ = other.name_;
        this->sex_ = other.sex_;
        this->score_ = other.score_;
    }

    void print(){
        birthday_.Birthdayprint();
        cout << "Name: " << name_ << endl;
        cout << "Sex: " << sex_ << endl;
        cout << "Score: " << score_ << endl;
    }
};


class Graduate: public Student{
private:
    float salary_;
public:
    Graduate(string name, char sex, float score, float salary, int year, int month, int day):Student(name, sex, score, year,  month,  day), salary_(salary){}

    Graduate(const Graduate& other):Student(other){
        cout<<" Graduate (const Graduate& other)"<<endl;
        this->salary_ = other.salary_;
    }
    void pri(){
        print();
        cout << "Salary: " << salary_ << endl;
    }
};

class Doctor: public Graduate{
private:
    string title_;
public:
    Doctor(string name, char sex, float score, float salary, int year, int month, int day, string title): Graduate(name, sex, score, salary, year, month, day), title_(title){}
    Doctor(const Doctor& other):Graduate(other){
        cout << " Doctor (const Doctor& other)" << endl;
        this->title_ = other.title_;
    }
    void Dpri(){
        pri();
        cout << "Title: " << title_ << endl;
    }
};


int main(){

    Graduate g("Alice", 'F', 95.5, 5000 , 2000, 1, 1);
    g.pri();
    cout <<"==============="<< endl;
    Doctor d("Bob", 'M', 85.0, 4000, 2111, 1, 1, "Doctor");
    d.Dpri();

    cout <<"==============="<< endl;


    Doctor d2(d);
    d2.Dpri();

    return 0;
}


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输出Birthday:2000/1/1
Name: Alice
Sex: F
Score: 95.5
Salary: 5000
===============
Birthday:2111/1/1
Name: Bob
Sex: M
Score: 85
Salary: 4000
Title: Doctor
===============
 Birthday (const Birthday& other)
 Student (const Student& other)
 Graduate (const Graduate& other)
 Doctor (const Doctor& other)
Birthday:2111/1/1
Name: Bob
Sex: M
Score: 85
Salary: 4000
Title: Doctor


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