赋值运算符函数

类型声明如下：

class CMyString
{
public:
	CMyString(char* pData = nullptr);
	CMyString(const CMyString& str);
	~CMyString(void);

	CMyString& operator = (const CMyString& str);

	void Print();

private:
	char* m_pData;
};

请为上类型添加赋值运算符函数.

经典解法：

CMyString& CMyString::operator = (const CMyString& str)
{
	if (this == &str)
		return *this;

	delete[]m_pData;
	m_pData = nullptr;

	m_pData = new char[strlen(str.m_pData) + 1];
	strcpy(m_pData, str.m_pData);

	return *this;
}

考虑异常安全性解法：

CMyString& CMyString::operator = (const CMyString & str) {
	if (this != &str) {
		CMyString strTemp(str);
		char * pTemp = strTemp.m_pData;
		strTemp.m_pData = m_pData;
		m_pData = pTemp;
	}
	return *this;
}

测试代码：

void CMyString::Print()
{
	printf("%s", m_pData);
}

void Test1()
{
	printf("Test1 begins:\n");

	char* text = "Hello world";

	CMyString str1(text);
	CMyString str2;
	str2 = str1;

	printf("The expected result is: %s.\n", text);

	printf("The actual result is: ");
	str2.Print();
	printf(".\n");
}

// 赋值给自己
void Test2()
{
	printf("Test2 begins:\n");

	char* text = "Hello world";

	CMyString str1(text);
	str1 = str1;

	printf("The expected result is: %s.\n", text);

	printf("The actual result is: ");
	str1.Print();
	printf(".\n");
}

// 连续赋值
void Test3()
{
	printf("Test3 begins:\n");

	char* text = "Hello world";

	CMyString str1(text);
	CMyString str2, str3;
	str3 = str2 = str1;

	printf("The expected result is: %s.\n", text);

	printf("The actual result is: ");
	str2.Print();
	printf(".\n");

	printf("The expected result is: %s.\n", text);

	printf("The actual result is: ");
	str3.Print();
	printf(".\n");
}

测试结果：