赋值运算符重载

#include
using namespace std;

class A
{
public:
	A(const char* s= "no data");
	void Show();
	~A();

private:
	char* str;
};


A::A(const char* s)
{
	str = new char[strlen(s) + 1];
	strcpy_s(str, strlen(s) + 1, s);
}

void A::Show()
{
	cout << str << endl;
}

A::~A()
{
	delete[] str;
}

int main()
{
	A* p = new A("hello world");
	A a1;
	a1 = *p;//这个只是单纯的属性值拷贝 a.str = p.str ,两个str指向了相同的地址
	a1.Show();//所谓的浅拷贝
	delete p;
	a1.Show();
	return 0;
}

#include
using namespace std;

class A
{
public:
	A(const char* s= "no data");
	A& operator=(const A& a);
	void Show();
	~A();

private:
	char* str;
};


A::A(const char* s)
{
	str = new char[strlen(s) + 1];
	strcpy_s(str, strlen(s) + 1, s);
}

A& A::operator=(const A& a)
{
	if (str != NULL)
	{
		delete[] str;
	}
	str = new char[strlen(a.str) + 1];
	strcpy_s(str, strlen(a.str) + 1, a.str);
	return *this;
}

void A::Show()
{
	cout << str << endl;
}

A::~A()
{
	delete[] str;
}

int main()
{
	A* p = new A("hello world");
	A a1;
	a1 = *p;
	a1.Show();
	delete p;
	a1.Show();
	return 0;
}