自定义string类

#include <iostream>
#include <cstring>
using namespace std;
class MyString
{
    public:
	    MyString(const char *pData = NULL);
	    MyString(const MyString &str);
	    MyString& operator = (const MyString &str);
	    void Show(){cout << "size:" <<size << " " << data << endl;}
	    ~MyString(){delete []data; data = NULL;}
	private:
		char *data;
		int size;
};
MyString::MyString(const char *pData)
{
	if(pData == NULL)
	{
		data = new char[1];
		*data = '\0';
		size = 0;
	}
	else
	{
		size = strlen(pData);
		data = new char[size+1];
		strcpy(data,pData);
	}
}
MyString::MyString(const MyString &str)
{
	size = str.size;
	data = new char[size+1];
	strcpy(data,str.data);
}
MyString& MyString::operator = (const MyString &str)
{
	if(this == &str)
	    return *this;
	    
	delete []data;
	data = NULL;
	size = str.size;
	data = new char[size+1];
	strcpy(data,str.data);
	
	return *this;
}
int main()
{
	MyString s1;
	char *p = "abcd";
	MyString s2(p);
	s1.Show();
	s1 = s2;
	s1.Show();
}