August 2021
Intermediate to advanced
450 pages
9h 36m
Chinese
Content preview from C++程序设计：原理与实践（基础篇）（原书第2版）
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9.4.6 报告错误
当我们发现一个非法日期时，应该做什么呢？检查非法日期的代码应该放在程序中什么位置呢？从5.6节我们可以得到第一个问题的答案是“抛出一个异常”，而放置检查代码的位置显然应该是我们最初构造一个Date对象时。如果没有创建非法的Date对象，而且成员函数也编写正确，那么我们就永远不会得到具有非法值的Date对象。因此，我们应该阻止用户创建具有非法状态的Date对象：
我们将合法性检查代码放到一个独立的函数is_valid（）中，这一方面是因为，从逻辑上讲，合法性检查与初始化就是不同的工作，另一方面是因为，我们可能需要多个构造函数。如你所见，除了私有数据外，我们还可以为类声明私有函数：
给出这样的Date定义后，我们可以写出如下代码：
我们现在知道，<<和add_day（）会获得一个合法的日期作为它们的操作对象。 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.