- C++(二十二)派生类的运算符重载
- 语法
- 赋值顺序
- 引例1:当子类,不自实现赋值运算符函数重载时,默认调用父类的赋值运算符函数
- 引例2:子类自实现赋值运算符函数重载,不做特殊处理时,只会调用父类的赋值运算符函数.
- 引例3:子类自实现赋值运算符函数重载,在函数体内调用父类的赋值运算符函数.
- 内嵌函数的赋值运算符函数
- 案例
C++ 派生类的运算符重载
赋值运算符函数不是构造器，所以可以继承，语法上就没有构造器那么严格。
语法
子类& 子类::operator=(const 子类& another)
{父类::operator =(another); // 调用父类的赋值运算符重载...
}
赋值顺序
引例1:当子类,不自实现赋值运算符函数重载时,默认调用父类的赋值运算符函数
//todo 派生类运算符重载
#include <iostream>
using namespace std;class A{public:int a;A(){cout << "A()" << endl;}A & operator=(const A& other){this->a=other.a;cout << " A & operator=(const A& other) " << endl;return *this;}
};class B: public A{
public:int b;B(){cout << "B()" << endl;}
};int main() {B b;B bb;b=bb;return 0;
}输出:
A()
B()
A()
B()A & operator=(const A& other)
引例2:子类自实现赋值运算符函数重载,不做特殊处理时,只会调用父类的赋值运算符函数.
//todo 派生类运算符重载
#include <iostream>
using namespace std;class A{
public:int a;A(){cout << "A()" << endl;}A & operator=(const A& other){this->a=other.a;cout << " A & operator=(const A& other) " << endl;return *this;}
};class B: public A{
public:int b;B(){cout << "B()" << endl;}B & operator=(const B& other){this->b=other.b;cout << " B & operator=(const A& other) " << endl;return *this;}};int main() {B b;B bb;b=bb;return 0;
}A()
B()
A()
B()B & operator=(const A& other)
引例3:子类自实现赋值运算符函数重载,在函数体内调用父类的赋值运算符函数.
//todo 派生类运算符重载
#include <iostream>
using namespace std;class A{
public:int a;A(int x){a=x;cout << "A()" << endl;}A & operator=(const A& other){if (this==&other){return *this;}this->a=other.a;cout << " A & operator=(const A& other) " << endl;return *this;}
};class B: public A{
public:int b;B(int x, int y):A(x){b=y;cout << "B()" << endl;}B & operator=(const B& other){if (this==&other){return *this;}//显示调用基类的赋值运算符A::operator=(other);this->b=other.b;cout << " B & operator=(const A& other) " << endl;return *this;}};int main() {B b(1,2);B bb(3,4);b=bb;cout << b.a << " " << b.b << endl;return 0;
}输出:
A()
B()
A()
B()A & operator=(const A& other)B & operator=(const A& other)
3 4
内嵌函数的赋值运算符函数
//todo 派生类运算符重载
#include <iostream>
using namespace std;class C{public:int c;C(int x){c=x;cout << "C()" << endl;}C & operator=(const C& other){if (this==&other){return *this;}this->c=other.c;cout << " C & operator=(const C& other) " << endl;return *this;}};class A{
public:int a;A(int x){a=x;cout << "A()" << endl;}A & operator=(const A& other){if (this==&other){return *this;}this->a=other.a;cout << " A & operator=(const A& other) " << endl;return *this;}
};class B: public A{
public:C c;int b;B(int x, int y , int z):A(x),c(z){b=y;cout << "B()" << endl;}B & operator=(const B& other){if (this==&other){return *this;}//显示调用内嵌函数c=other.c;//显示调用基类的赋值运算符A::operator=(other);//赋值兼容:this->b=other.b;cout << " B & operator=(const A& other) " << endl;return *this;}};int main() {B b(1,2,99);B bb(3,4,77);b=bb;cout << b.a << " " << b.b << " " << b.c.c <<endl;return 0;
}输出:
A()
C()
B()
A()
C()
B()C & operator=(const C& other)A & operator=(const A& other)B & operator=(const A& other)
3 4 77
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_;}Birthday & operator=(const Birthday& other){if (this==&other){return *this;}this->year_ = other.year_;this->month_ = other.month_;this->day_ = other.day_;cout << " Birthday & operator=(const Birthday& other) " << endl;return *this;}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_;}Student & operator=(const Student& other){if (this==&other){return *this;}this->name_ = other.name_;this->sex_ = other.sex_;this->score_ = other.score_;//显示调用基类的赋值运算符函数this->birthday_ = other.birthday_;cout << " Student & operator=(const Student& other) " << endl;return *this;}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_;}Graduate & operator=(const Graduate& other){if (this==&other){return *this;}//显示调用基类的赋值运算符函数Student::operator=(other);this->salary_ = other.salary_;cout << " Graduate & operator=(const Graduate& other) " << endl;return *this;}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_;}Doctor & operator=(const Doctor& other){if (this==&other){return *this;}//显示调用基类的赋值运算符函数Graduate::operator=(other);this->title_ = other.title_;cout << " Doctor & operator=(const Doctor& other) " << endl;return *this;}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();cout <<"#####################"<< endl;Doctor n1("Bob", 'M', 85.0, 9900, 666, 6, 6, "Doctor");Doctor n2("sadsdw", 'G', 1111.0, 4000, 77, 7, 7, "7777");n2=n1;n2.Dpri();return 0;
}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
#####################Birthday & operator=(const Birthday& other)Student & operator=(const Student& other)Graduate & operator=(const Graduate& other)Doctor & operator=(const Doctor& other)
Birthday:666/6/6
Name: Bob
Sex: M
Score: 85
Salary: 9900
Title: Doctor
