对象赋值的语义

若未声明或实现该赋值操作符，编译器将自动生成一个默认赋值操作符。

实现类似以下代码：

TPoint2D::operation = (const TPoint2D& source)
{
    this->xcoordinate = source.xcoordinate;
    this->ycoordinate = source.ycoordinate;
    return *this;
}

实现： 1 TPoint2D::operation = (const TPoint2D& source 2 {

    if (this == &source)//自我赋值检查
        return *this;
    this->ssn = source.ssn;
    //接下来，需要赋值name中的字符
    //如果name中空间充足，则只需复制字符即可
    //否则，删除name所指向的现有内存，然后分配新的内存块
    //最后，复制字符.
    if (source.name != 0)
    {
        int nameLength = strlen(source.name);
        int thisNameLength = (this->name) ? strlen(this->name) : 0;
        if (nameLength <= thisNameLength)
            strcpy(this->name, source.name);
        else
        {
            delete[]this->name;
            name = new char[nameLength + 1];
            strcpy(this->name, source.name);
        }
    }
    else
    {
        delete[]this->name; this->name = 0;
    }
    //address重复上面的步骤完成
　　return *this;
}