大扑棱蛾子的个人博客

定义

里氏替换原则是Barbara Liskov^[1]与1988年提出来的。原文是：

What is wanted here is something like the following substitution property: If for each object of type S there is an object of type T such that for all programs P defined in terms of T, the behavior of P is unchanged when is substituted for then S is a subtype of T

如果对每一个类型为$S$的对象$O_1$， 都有类型为$T$的对象$O_2$， 使得以T定义的所有程序P在所有的对象$O_1$都代换成$O_2$时， 程序 P 的行为没有发生变化， 那么类型$S$是类型$T$的子类型。

另一种说法是：

Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it.

所有引用基类的地方必须能透明地使用其子类的对象。