String类的编写

String类的编写

1，const & class 可以调用私有成员

2. 友元函数重载

class MyString
{
public:
    MyString(char * s = NULL)
    {
        if(s != NULL)
        {
            int size = strlen(s) + 1;
            m_str = new char[size];
            strcpy(m_str, s);
        }
        else m_str = NULL;
    }
    MyString(const MyString & other)
    {
        if(other.m_str != NULL)
        {
            int size = strlen(other.m_str) + 1;
            m_str = new char[size];
            strcpy(m_str,other.m_str);
        }
    }
    MyString & operator = (const MyString & other)
    {
        if(m_str == other.m_str)
            return *this;
        delete []m_str;
        if(other.m_str != NULL)
        {
            int size = strlen(other.m_str) + 1;
            m_str = new char[size];
            strcpy(m_str,other.m_str);
        }
        return *this;
    }
    ~MyString()
    {
        if(m_str != NULL)
        delete []m_str;
    }
    friend ostream & operator<<(ostream &o,const MyString &str)
    {
        o << str.m_str ;
        return o;
    }
private:
    char * m_str;
};

代码。