26、C++ 编程：虚拟析构函数、多重继承与链表的深入解析

C++ 编程：虚拟析构函数、多重继承与链表的深入解析

1. 虚拟析构函数

在使用动态内存时，完成操作后需使用 delete 释放内存。以 Text 对象为例，其实现如下：

//Text class, for use with the SSDL library
#ifndef TEXT_H
#define TEXT_H
#include "shape.h"
class Text: public Shape
{
 public:
    Text (const char* txt = "")    { copy (txt);      }
    Text (const Text& other) : Shape (other)
    {
        copy (other.contents_);
    }
    Text (int x, int y, const char* txt = "") : Shape(x, y)
    {
        copy(txt);
    }
    ~Text () override { if (contents_) delete contents_; }
    const Text& operator=(const Text& other);
    const char* contents () const { return contents_; }
    void drawAux         () const override
    {
        SSDL_RenderText (conten