C++中=号的重载以及=号赋值与赋值构造函数的区别

=重载与使用复制构造一样需要重新为对象分配内存，并且需要注意如果对象没有被提前创建而是采用了MySring L=M;的形式系统还是会采用复制构造而不是=重载；

class MyString {
private:
	char*str;
	int len;
public:
	MyString() {};
	MyString(const char*str);
	void disp();
	MyString&operator=(const MyString&S);
	void SetStr(int i, char c);
};

void MyString::SetStr(int i, char c)
{
	str[i] = c;
}

MyString&MyString::operator=(const MyString&S)
{
	if (len < S.len) { len = S.len;delete[]str;str = new char[S.len + 1]; }
	int i;
	for (i = 0;i < S.len;i++)
		str[i] = S.str[i];
	str[i] = '\0';
	return *this;
}

void MyString::disp()
{
	cout << str << endl;
	cout << len << endl;
}

MyString::MyString(const char*str)
{
	this->str = new char[strlen(str) + 1];
	int i;
	for (i = 0;i < strlen(str);i++)
		(this->str)[i] = str[i];
	(this->str)[i] = '\0';
	len = strlen(str);
}

int main()
{
	MyString S("hello");
	MyString M;
	M = S;//引用的是=
	MyString L = S;//会引用复制构造
	cout << "S:";
	S.disp();
	cout << "M:";
	M.disp();
	cout << "L:";
	L.disp();
	M.SetStr(0, 'H');
	cout << "S:";
	S.disp();
	cout << "M:";
	M.disp();
	cout << "L:";
	L.disp();
	system("pause");
}