是否有充分的理由说明在函数中只有一个return语句是一个更好的实践?
或者在逻辑上正确的情况下,可以从函数中返回,这意味着函数中可能有许多返回语句?
是否有充分的理由说明在函数中只有一个return语句是一个更好的实践?
或者在逻辑上正确的情况下,可以从函数中返回,这意味着函数中可能有许多返回语句?
当前回答
这可能是一个不寻常的观点,但我认为任何相信多个return语句是有利的人都从未在只支持4个硬件断点的微处理器上使用过调试器。:-)
虽然“箭头代码”的问题是完全正确的,但当使用多个return语句时,一个问题似乎消失了,那就是在使用调试器的情况下。您没有一个方便的万能位置来放置断点,以保证您将看到退出,从而看到返回条件。
其他回答
正如Kent Beck在《实现模式》中讨论保护子句时指出的那样,使一个例程具有单一的入口和出口点……
是为了防止可能的混淆 当你在许多地方跳来跳去 同一例程中的位置。这让 当应用到FORTRAN或 汇编语言程序 有大量的全球数据,甚至 理解哪些语句是 执行是一项艰苦的工作……使用小方法和大部分本地数据,它是不必要的保守。”
我发现用保护子句编写的函数要比一长串嵌套的if then else语句容易理解得多。
你知道有句谚语——情人眼里出西施。
有些人信得过NetBeans,有些人信得过IntelliJ IDEA,有些人信得过Python,有些人信得过PHP。
在一些商店,如果你坚持这样做,你可能会丢掉工作:
public void hello()
{
if (....)
{
....
}
}
这个问题完全是关于可见性和可维护性。
I am addicted to using boolean algebra to reduce and simplify logic and use of state machines. However, there were past colleagues who believed my employ of "mathematical techniques" in coding is unsuitable, because it would not be visible and maintainable. And that would be a bad practice. Sorry people, the techniques I employ is very visible and maintainable to me - because when I return to the code six months later, I would understand the code clearly rather seeing a mess of proverbial spaghetti.
嘿,伙计(就像一个前客户曾经说过的),做你想做的,只要你知道如何在我需要你解决它的时候解决它。
I remember 20 years ago, a colleague of mine was fired for employing what today would be called agile development strategy. He had a meticulous incremental plan. But his manager was yelling at him "You can't incrementally release features to users! You must stick with the waterfall." His response to the manager was that incremental development would be more precise to customer's needs. He believed in developing for the customers needs, but the manager believed in coding to "customer's requirement".
我们经常因为打破数据规范化、MVP和MVC边界而感到内疚。我们内联而不是构造函数。我们走捷径。
就我个人而言,我认为PHP是一种糟糕的实践,但我又知道什么呢?所有的理论争论都归结为试图满足一套规则
质量=精度,可维护性 和盈利能力。
所有其他规则都退居幕后。当然,这条规则永远不会消失:
懒惰是一种美德 程序员。
Well, maybe I'm one of the few people here old enough to remember one of the big reasons why "only one return statement" was pushed so hard. It's so the compiler can emit more efficient code. For each function call, the compiler typically pushes some registers on the stack to preserve their values. This way, the function can use those registers for temporary storage. When the function returns, those saved registers have to be popped off the stack and back into the registers. That's one POP (or MOV -(SP),Rn) instruction per register. If you have a bunch of return statements, then either each one has to pop all the registers (which makes the compiled code bigger) or the compiler has to keep track of which registers might have been modified and only pop those (decreasing code size, but increasing compilation time).
今天仍然坚持使用一个return语句的一个原因是易于自动重构。如果您的IDE支持方法提取重构(选择一系列行并将它们转换为一个方法),那么如果您想提取的行中有一个return语句,特别是如果您正在返回一个值,则很难做到这一点。
如果你最终得到了很多返回值,那么你的代码可能有问题。否则,我同意有时能够从子例程的多个位置返回是很好的,特别是当它使代码更干净的时候。
Perl 6:坏例子
sub Int_to_String( Int i ){
given( i ){
when 0 { return "zero" }
when 1 { return "one" }
when 2 { return "two" }
when 3 { return "three" }
when 4 { return "four" }
...
default { return undef }
}
}
这样写会更好吗
Perl 6:好例子
@Int_to_String = qw{
zero
one
two
three
four
...
}
sub Int_to_String( Int i ){
return undef if i < 0;
return undef unless i < @Int_to_String.length;
return @Int_to_String[i]
}
注意,这只是一个简单的例子
我更喜欢一个return语句。一个尚未指出的原因是,一些重构工具在单点退出时工作得更好,例如Eclipse JDT提取/内联方法。