![[置顶] 运算符重载 浅拷贝(logical copy) vs 深拷贝(physical copy) 三大件（bigthree problem）...](https://700zi.400zi.cn/uploadfile/img/15/882/ed1cc484077b5211a2c611dd4e370334.jpg)
一般的我们喜欢这样对对象赋值：
Person p1;Person p2=p1;
classTobject(another_object),orAa(b);
classTobject=anotherobject;
classA
{
//…
};
intmain()
{
Ax;
Ay(x);
//…
Az=x;
z=y;
}
这样的话，如果成员变量中有指针的话，就容易造成指针的二次删除。这样就需要我们显示的在类中实现
1、拷贝构造，
2、赋值运算符重载。
1）、判断是不是自赋值，2）、释放旧空间，3）、开辟新空间。4）、内容本身的 拷贝，5）、返回*this
3、析构函数（释放指针指向的空间）。
这三步使类实现深拷贝，从而避免浅拷贝的二次删除问题。俗称三大件。
classVector
{
private:
int*rep;
intsize;
voidclone(constVector&a);
voiddispose();
public:
Vector(ints=0);
//adefaultconstructorinitializingallmembersofrepto0ifsisnot0.
Vector(int*,int);
//aconstructorcreatesaVectorobjectfromanordinaryarray
Vector(constVector&v); //acopyconstructor
~Vector(){dispose();} //adestructor
intget_size()const{returnsize;} //anaccessor
constVector&operator=(constVector&x);
int&operator[](intindex){returnrep[index];}
constint&operator[](intindex)const{returnrep[index];}
};
//Vectorv;
//V=a;
//Vectorv(a);
voidVector::clone(constVector&a)
{
this->size=a.size;rep=newint[size];
for(intcount=0;count<size;++count)
rep[count]=a[count];//(*this)[count]=a[count];
//rep[count]=a.rep[count];
}
voidVector::dispose()
{
delete[]rep;
rep=NULL;
}
Vector::Vector(ints):size(s)
{
if(size<=0)
{rep=NULL;}
else
{
rep=newint[size];
for(intcount=0;count<size;++count)
{rep[count]=0;}}
}
Vector::Vector(int*a,ints):size(s),rep(newint[s])
{
for(intcount=0;count<size;++count)
{rep[count]=a[count];}
}
Vector::Vector(constVector&v)
{clone(v);}
//forexample:Vectora,v;a.=(v);
constVector&Vector::operator=(constVector&x)
{
if(this!=&x)//Vectorv;Vector*p=&v;v=*p;
{
delete[]rep;
this->size=x.size;
rep=newint[size];
for(intcount=0;count<size;++count)
rep[count]=x[count];
}
return*this;
}
//overloadingoperator<<,notafriendfunction
ostream&operator<<(ostream&out,constVector&x)
{
ints=x.get_size();
for(inti=0;i<s;++i)
{
out<<x[i]<<endl;//out<<x.rep[i]<<endl;
}
out<<endl;
returnout;
}
booloperator==(constVector&a,constVector&b)
{
boolyes=true;
if(a.get_size()!=b.get_size())
{yes=false;}
else
{
ints,index=0;
s=a.get_size();
while(index<s&&a[index]==b[index])
{++index;}
if(index<s)
{yes=false;}
}
returnyes;
}
intmain()
{
Vectervec1;
cout<<vec1<<endl;
intarray[5]={1,2,3,4,5};
Vectorvec2(array,5);
cout<<vec2<<endl;
Vectorvec3(vec2);
cout<<vec3<<end;
if(vec3==vec2)
{
Cout<<”Thevector3isequaltovector2”<<endl;
}
Vectorvec4;
vec4=vec3;
cout<<vec4<<end;
return0;
}
#include <iostream>using namespace std;class String{public:String(char* c=""):len(strlen(c)){if(!c){str=new char[1];strcpy(str,"");}else{str=new char[strlen(c)+1];strcpy(str,c);}}String(const String& s){len=s.len;if(!s.str){str=new char[1];strcpy(str,"");}else{str=new char[len+1];strcpy(str,s.str);}}~String(){if(str){delete []str;str=NULL;}}const String& operator=(const String& s){if(this!=&s){len=s.len;delete str;if(!s.str){str=new char[1];strcpy(str,"");}else{str=new char[len+1];strcpy(str,s.str);}}return *this;}const char& operator[](int index)const{return str[index];}char& operator[](int index){return str[index];}bool operator==(const String& s){if(len!=s.len)return false;while (len--){if((*this)[len]!=s[len])return false;}return true;}const String operator+(const String& s){char* p=new char[len+s.len+1];strcpy(p,str);strcat(p,s.str);String newStr(p);return newStr;}friend ostream& operator<<(ostream& out,const String & s);friend istream& operator>>(istream& in, String & s);private:int len;char* str;};ostream& operator<<(ostream& out,const String & s){out<<s.str<<" "<<s.len<<endl;return out;}istream& operator>>(istream& in,String & s){cout<<"请输入小于100的字符串"<<endl;delete s.str;s.str=new char[100];in>>s.str;s.len=strlen(s.str);return in;}int main(){String s1,s2;cin>>s1;cin>>s2;cout<<(s1==s2)<<endl;cout<<"s1+s2"<<endl;cout<<(s1+s2)<<endl;s1=s2;cout<<s1<<" s2= "<<s2;cout<<(s1==s2)<<endl;return 0;}
.写一个学生类，从person类继承，增加的属性为成绩f和评语label（字符串）。
person: name,age,print(),要求使用三大件，输出重载，==重载，下标重载。
#include<iostream>#include<string.h>using namespace std;class Person{friend ostream& operator<<(ostream& out,Person& p);public:Person(int a ,char * c):age(a){if(!c){name=NULL;}else{name=new char[strlen(c)+1];strcpy(name,c);}}Person(Person& p){if(!p.name){name=NULL;}else{name=new char[strlen(p.name)+1];strcpy(name,p.name);}}~Person(){if(name!=NULL)delete []name;}const Person& operator=(Person& p){if(this!=&p){delete[]name;name=new char[strlen(p.name)+1];strcpy(name,p.name);}return *this;}void print(){cout<<*this;}protected:int age;char* name;};ostream& operator<<(ostream& out,Person& p){out<<"姓名："<<p.name<<" 年龄:"<<p.age<<endl;return out;}class Student:public Person{friend ostream& operator<<(ostream& out,Student& s);public:Student(int a,char* n,float fl=0,char* c=""):Person(a,n),f(fl){if(!c){lable=NULL;}else{lable=new char[strlen(c)+1];strcpy(lable,c);}}Student(Student& s):Person(s){if(!s.lable){f=s.f;lable=NULL;lable=new char[strlen(s.lable)+1];strcpy(lable,s.lable);}}~Student(){if(lable!=NULL)delete[] lable;}const Student& operator=(Student& s){if(this!=&s){Person::operator=(s);if(!s.lable){f=s.f;lable=NULL;}else{f=s.f;delete[]lable;lable=new char[strlen(s.lable)+1];strcpy(lable,s.lable);}}}void print(){cout<<*this;}private:float f;char* lable;};ostream& operator<<(ostream& out,Student& s){out<<"姓名："<<s.name<<" 年龄:"<<s.age<<endl;out<<"成绩："<<s.f<<" 评语:"<<s.lable<<endl;return out;}int main(){Person *p=new Person(18,"小方");p->print();Student* s=new Student(18,"小芳",99,"山上有个姑娘叫小芳");s->print();Person* p2=s;p2->print();((Student*)p2)->print();(*((Student*)p2)).print();Student s1(99,"阿黄",99,"上有个姑娘叫阿黄");Person& p3=s1;p3.print();s1.print();((Student&)p3).print();return 0;}
1. Person为基类：虚函数为 dailywork() ~Person()
定义三个子类：Student Doctor(char* label) Driver(char* label)
主函数：定义基类指针数组，动态创建子类对象，调用成员函数，删除创建的对象
#include<iostream.h>
#include<string.h>
class Person
{
friend ostream& operator<<(ostream& out,Person& p);
public:
Person(int a =0,char * c=""):age(a)
{
if(!c)
{
name=NULL;
}
else
{
name=new char[strlen(c)+1];
strcpy(name,c);
}
}
Person(const Person& p)
{
if(!p.name)
{
name=NULL;
}
else
{
name=new char[strlen(p.name)+1];
strcpy(name,p.name);
}
}
virtual~Person()
{
if(name!=NULL)
delete []name;
}
virtual void dailywork()
{
cout<<"<^.^> 吃饭 劳动 睡觉 活下去 <^.^>";
}
const Person& operator=(const Person& p)
{
if(this!=&p)
{
delete[]name;
name=new char[strlen(p.name)+1];
strcpy(name,p.name);
}
return *this;
}
void print()
{
cout<<*this;
}
protected:
int age;
char* name;
};
ostream& operator<<(ostream& out,Person& p)
{
out<<"姓名："<<p.name<<" 年龄:"<<p.age<<endl;
return out;
}
class Student:public Person
{
friend ostream& operator<<(ostream& out,Student& s);
public:
Student(int a,char* n,float fl=0,char* c=""):Person(a,n),f(fl)
{
if(!c)
{
lable=NULL;
}
else
{
lable=new char[strlen(c)+1];
strcpy(lable,c);
}
}
Student(Student& s):Person(s)
{
if(!s.lable)
{
f=s.f;
lable=NULL;
lable=new char[strlen(s.lable)+1];
strcpy(lable,s.lable);
}
}
~Student()
{
if(lable!=NULL)
delete[] lable;
}
void dailywork()
{
Person::dailywork();
cout<<"<^.^> 学习 学习 再学习 <^.^>"<<endl;
}
const Student& operator=(const Student& s)
{
if(this!=&s)
{
Person::operator=(s);
if(!s.lable)
{
f=s.f;
lable=NULL;
}
else
{
f=s.f;
delete[]lable;
lable=new char[strlen(s.lable)+1];
strcpy(lable,s.lable);
}
}
}
void print()
{
cout<<*this;
}
private:
float f;
char* lable;
};
ostream& operator<<(ostream& out,Student& s)
{
out<<"姓名："<<s.name<<" 年龄:"<<s.age<<endl;
out<<"成绩："<<s.f<<" 评语:"<<s.lable<<endl;
return out;
}
class Doctor:public Person
{
public:
Doctor(int _age,char *_name,char* _lable):Person(_age,_name)
{
if(!_lable)
{
lable=new char[1];
strcpy(lable,"");
}
else
{
lable=new char[strlen(_lable)+1];
strcpy(lable,_lable);
}
}
Doctor(const Doctor& d):Person(d)
{
if(!d.lable)
{
lable=NULL;
}
else
{
lable=new char[strlen(d.lable)+1];
strcpy(lable,d.lable);
}
}
~Doctor()
{
if(lable)
{
delete []lable;
lable=NULL;
}
}
const Doctor& operator=(const Doctor& d)
{
if(this!=&d)
{
Person::operator=(d);
if(!d.lable)
{
lable=NULL;
}
else
{
lable=new char[strlen(d.lable)+1];
strcpy(lable,d.lable);
}
}
return *this;
}
void dailywork()
{
Person::dailywork();
cout<<"<^.^> 救死 扶伤 治病 抓药 <^.^>"<<endl;
}
private:
char* lable;
friend const ostream& operator<<(ostream& out,const Doctor & d);
};
const ostream& operator<<(ostream& out,const Doctor& d)
{
out<<(Person&)d<<endl;
out<<d.lable<<endl;
return out;
}
class Driver:public Person
{
public:
Driver(int _age,char *_name,char* _lable):Person(_age,_name)
{
if(!_lable)
{
lable=new char[1];
strcpy(lable,"");
}
else
{
lable=new char[strlen(_lable)+1];
strcpy(lable,_lable);
}
}
Driver(const Driver& d):Person(d)
{
if(!d.lable)
{
lable=NULL;
}
else
{
lable=new char[strlen(d.lable)+1];
strcpy(lable,d.lable);
}
}
~Driver()
{
if(lable)
{
delete []lable;
lable=NULL;
}
}
const Driver& operator=(const Driver& d)
{
if(this!=&d)
{
Person::operator=(d);
if(!d.lable)
{
lable=NULL;
}
else
{
lable=new char[strlen(d.lable)+1];
strcpy(lable,d.lable);
}
}
return *this;
}
void dailywork()
{
Person::dailywork();
cout<<"<^.^> 驾驶 开车 拉货 跑四方 <^.^>"<<endl;
}
private:
char* lable;
friend const ostream& operator<<(ostream& out,const Driver & d);
};
const ostream& operator<<(ostream& out,const Driver & d)
{
out<<(Person&)d<<endl;
out<<d.lable<<endl;
return out;
}
int main()
{
Person *p=new Person(18,"小方");
p->print();
Student* s=new Student(18,"小芳",99,"山上有个姑娘叫小芳");
s->print();
Person* p2=s;
p2->print();
((Student*)p2)->print();
(*((Student*)p2)).print();
Student s1(99,"阿黄",99,"上有个姑娘叫阿黄");
Person& p3=s1;
p3.print();
s1.print();
((Student&)p3).print();
cout<<"====//开始====="<<endl;
Person array[3]={Person(30,"张二狗"),Person(18,"二凤"),Person(18,"Mis Y")};
Person *parray[3];
parray[0]=array;
parray[1]=array+1;
parray[2]=array+2;
parray[0]->dailywork();
array[0].dailywork();
cout<<"========="<<endl;
parray[0]=new Student(20,"张三",99,"好学生");
parray[1]=new Driver(22,"李四","好司机");
parray[2]=new Doctor(30,"王五","好大夫");
for(int i=0;i<3;i++)
{
parray[i]->dailywork();
delete []parray[i];
}
//Student sarry();
//Student** sParry=new Student *[2];
//delete []sParry;
return 0;
}
