不区分交换机这样的工作？ [英] Does case-switch work like this?

问题描述

我碰到$ C $今天C的情况下，开关件，是有点惊讶地看到它是如何worked.The code是

I came across a case-switch piece of code today and was a bit surprised to see how it worked.The code was

switch (blah)
{
case a:


           break;

case b:
           break;
case c:
case d:
case e: 
  {
code here
  }
  break;
default :
   return;
}

要我在变量是c中的路径场景惊喜code在这里里面去了。我段同意存在的情况下开关的C部分的结束没有中断，但我将不得不想象的要经过默认instead.When你降落在一个案例胡说：行犯规检查它，如果你的当前值的具体情况相匹配的才把让你在特定的细分，否则有什么？有一个情况呢？

To my surprise in the scenario where variable was c the path went inside the "code here" segment .I agree there is no break at the end of the 'c' part of the case switch but i would have imagined it to go through default instead.When you land at a "case blah : " line doesnt it check if your current value matches the particular case and only then let you in the specific segment?Otherwise what's the point of having a case?

推荐答案

这就是所谓案例落空，是一个理想的行为。它可以让你分享案例之间code。

This is called case fall-through, and is a desirable behavior. It allows you to share code between cases.

如何使用的情况下落空行为的一个例子：

An example of how to use case fall-through behavior:

switch(blah)
{
case a:
  function1();
case b:
  function2();
case c:
  function3();
  break;
default:
  break;
}

如果你输入的开关时，等等== A ，那么你将执行功能1（），函数2（）和 function3（）。

If you enter the switch when blah == a, then you will execute function1(), function2(), and function3().

如果你不希望有这种行为，可以通过包括退出它破语句。

If you don't want to have this behavior, you can opt out of it by including break statements.

switch(blah)
{
case a:
  function1();
  break;
case b:
  function2();
  break;
case c:
  function3();
  break;
default:
  break;
}

switch语句的工作方式是，它会（或多或少）执行转到跳转到您的case标签，并保留从该点运行。当执行击中破，它留下的开关组。

The way a switch statement works is that it will (more or less) execute a goto to jump to your case label, and keep running from that point. When the execution hits a break, it leaves the switch block.

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