继承是C++语言的三大特点之一。继承(或者说派生)机制的作用主要是用于代码的重用和扩展。
三种派生方式(public,protect,private)的访问控制
基类的控制类型 派生方式 派生类的控制类型
public ········································public
protect ··················public protect
private ——
public ··········································protect
protect··················· protect protect
private ············································ ——
public ·····private
protect ····················private private
private ——
上面列出了不同派生方式得到的派生类有着不同的访问控制情况。比如,基类的public成员经过protect方式的派生,在派生类中会变成protect成员,即派生类成员可以访问该成员,而类外的派生类对象不能访问它,以此类推。