89.赋值重载以及深浅拷贝
- 非指针,则深浅拷贝都一样,含有指针则内存共享,指针一致,内容一直
- 深拷贝,指针不一致,内存一直,内存是独享的
- 赋值重载如果有返回自身类型对象,会调用拷贝构造,需要重载拷贝构造,这一点是必须要注意的,原理是:先操作一个类,再把操作的这个类拷贝到本类中,即使返回(*this),也会调用 (如果返回值是自身类型,赋值重载的this指针是不是本类的this指针!!!!所以需要拷贝构造)
代码示例:
1 #define _CRT_SECURE_NO_WARNINGS 2 #include <iostream> 3 using namespace std; 4 5 //非指针,则深浅拷贝都一样,含有指针则内存共享,指针一致,内容一直 6 //深拷贝,指针不一致,内存一直,内存是独享的 7 //赋值重载如果有返回自身类型对象,会调用拷贝构造 8 //原理是:先操作一个类,再把操作的这个类拷贝到本类中,即使返回(*this),也会调用 9 10 class mystring 11 { 12 public: 13 char *p; 14 int n; 15 mystring() :p(nullptr), n(0) 16 { 17 18 } 19 20 mystring(char *str) 21 { 22 cout << "构造函数调用" << endl; 23 n = strlen(str) + 1; 24 p = new char[n]; 25 strcpy(this->p, str);//拷贝 26 } 27 28 mystring(const mystring &my) 29 { 30 cout << "拷贝构造函数调用" << endl; 31 cout << (void *)p << endl; 32 this->n = my.n; 33 this->p = new char[this->n]; 34 strcpy(this->p, my.p);//拷贝 35 } 36 37 ////重载= 38 //void operator =(const mystring &stringmy) 39 //{ 40 // delete this->p; 41 // cout << "赋值重载调用" << endl; 42 // this->n = stringmy.n; 43 // this->p = new char[this->n]; 44 // strcpy(this->p, stringmy.p); 45 //} 46 47 //使可以多次重载 48 mystring operator =(const mystring &stringmy) 49 { 50 cout << "赋值重载调用" << endl; 51 delete this->p; 52 this->n = stringmy.n; 53 this->p = new char[this->n]; 54 cout << (void *)p << endl; 55 strcpy(this->p, stringmy.p); 56 return (*this); 57 } 58 59 ~mystring() 60 { 61 delete this->p; 62 } 63 }; 64 65 void main() 66 { 67 mystring my1("12345"); 68 mystring my2,my3; 69 //赋值重载 70 my3 = my2 = my1; 71 cout << my3.p << endl; 72 cin.get(); 73 }
