C++下重写=号运算符解决浅拷贝问题

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
//#define _CRT_SECURE_NOWARNINGS
#pragma warning( disable : 4996) // 避免安全检查 一般超过2010版本的VS都会出现

#include<iostream>
using namespace std;

class Mystring {
public:
	// 无参构造
	Mystring() {
		this->m_data = NULL;
	}
	// 有参构造(str不能设置为默认值，否则调用无参构造时会冲突)
	Mystring(const char *str) {
		this->m_data = (char*)malloc(strlen(str) + 1); // 加1是字符串自动补0
		strcpy(this->m_data, str);
	}
	// 拷贝构造
	Mystring(const Mystring &other){
		this->m_data = (char*)malloc(strlen(other.m_data) + 1);
		strcpy(this->m_data, other.m_data);
	}
	// 重写等号运算符
	Mystring& operator=(Mystring &other){
		// 1 如果是自身 返回自身
		if (this == &other) {
			return *this;
		}
		// 2 如果自己原来的内存没有释放 那就释放
		if (this->m_data != NULL) {
			delete this->m_data;
		}
		// 3 开始进行深拷贝
		this->m_data = (char*)malloc(strlen(other.m_data) + 1);
		strcpy(this->m_data, other.m_data);
		// 4 返回自身
		return *this;
	}
	char* GetData() {
		if (this->m_data == NULL) {
			cout << "m_data is NULL" << endl;
			return (char*)"0";
		}
		return this->m_data;
	}
	~Mystring() {
		if (this->m_data != NULL) {
			delete this->m_data;
			this->m_data = NULL;
		}
	}
private:
	char *m_data;
};

int main() {

	Mystring a;
	cout << a.GetData() << endl;
	Mystring b("123");
	cout << b.GetData() << endl;
	Mystring c(b);
	cout << c.GetData() << endl;
	Mystring d = c;
	cout << d.GetData() << endl;

	return 0;
}