oral_quiz->#为类型添加赋值运算符#

//AssignmentOperator.cpp(little changed)
#include "std.h"

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

	CMyString& operator = (const CMyString& str);

	void Print();

private:
	char* m_pData;
};

CMyString::CMyString(char* pData) {
	if(pData == NULL) {
		m_pData = new char[1];
		m_pData[0] = '\0';
	}
	else {
		int length = strlen(pData);
		m_pData = new char[length + 1];
		strcpy(m_pData, pData);
	}
}

CMyString::CMyString(const CMyString& str) {
	int length = strlen(str.m_pData);
	m_pData = new char[length + 1];
	strcpy(m_pData, str.m_pData);
}

CMyString::~CMyString() {
	delete[] m_pData;
}

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 = "Nicholas";

	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 = "Nicholas";

	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 = "Nicholas";

	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");
}

int _tmain(int argc, _TCHAR* argv[]) {
	Test1();
	Test2();
	Test3();

	return 0;
}