编写类String的构造函数、析构函数和赋值函数

#include <iostream>

using namespace std;
class String
{
public:
String(const char *str = NULL);
String(const String &other);
~String(void);
String& operator =(const String &other);
// private:
char *m_data;//为了测试，暂时设为public
};
String::String(const char *str)
{

if(str == NULL)
{
m_data = new char[1];
*m_data = '/0';
}
else
{
int len = strlen(str);
m_data = new char[len+1];
strcpy(m_data,str);
}
}
String::~String(void)
{
if(m_data != NULL)
{
delete[] m_data;
}
}
String::String(const String &other)
{
if(*(other.m_data)=='/0')
{
m_data = new char[1];
*m_data = '/0';
}
else
{
int len = strlen(other.m_data);
m_data = new char[len+1];
strcpy(m_data,other.m_data);
}
}
String& String::operator =(const String &other)
{
if(this == &other)
return *this;
delete[] m_data;
m_data = new char[strlen((other.m_data)+1)];
strcpy(m_data,other.m_data);
return *this;
}
int main()
{
String s("sdlfkjsldkfjlsdjf");
String a(s);
String b = a;
cout<<s.m_data<<endl<<a.m_data<<endl<<b.m_data;
system("pause");
}