String的运算符重载

String的运算符重载

主要对String类的=、< 、>、==、+、>>运算符进行重载

示例

class String {

public:
    String(const char* p = nullptr)
    {
        if (p != nullptr)
        {
            _pstr = new char[strlen(p) + 1];
            strcpy(_pstr, p);
        }
        else
        {
            _pstr = new char[1];
            *_pstr = '\0';
        }
    }

    String(const String& rhs)
    {
        _pstr = new char[strlen(rhs._pstr) + 1];
        strcpy(_pstr, rhs._pstr);
    }

    String& operator=(const String& rhs)
    {
        if (this == &rhs)
            return *this;
        delete[]_pstr;
        _pstr = new char[strlen(rhs._pstr) + 1];
        strcpy(_pstr, rhs._pstr);
        return *this;
    }
    
    bool operator<(const String& rhs)
    {
        return strcmp(_pstr, rhs._pstr) < 0;
    }
    bool operator>(const String& rhs)
    {
        return strcmp(_pstr, rhs._pstr) > 0;
    }
    bool operator==(const String& rhs)
    {
        return strcmp(_pstr, rhs._pstr) == 0;
    }

    String operator+(const String& str)
    {
        char* pstr = new char[strlen(_pstr) + strlen(str._pstr) + 1];
        strcpy(pstr, _pstr);
        strcat(pstr, str._pstr);
        String tmp(pstr);
        delete[]pstr;

        return tmp;
    }
    char& operator[](int i)
    {
        return _pstr[i];
    }
    const char& operator[](int i)const
    {
        return _pstr[i];
    }
    friend ostream& operator <<(ostream& out, const String& str);
   
    ~String()
    {
        delete[]_pstr;
        _pstr = nullptr;
    }

private:
    char* _pstr;
};


ostream& operator <<(ostream& out, const String& str)
{
    out << str._pstr;    
    return out;
}