I lean towards using guard clauses to return early and otherwise exit at the end of a method. The single entry and exit rule has historical significance and was particularly helpful when dealing with legacy code that ran to 10 A4 pages for a single C++ method with multiple returns (and many defects). More recently, accepted good practice is to keep methods small which makes multiple exits less of an impedance to understanding. In the following Kronoz example copied from above, the question is what occurs in //Rest of code...?:

void string fooBar(string s, int? i) {

  if(string.IsNullOrEmpty(s) || i == null) return null;

  var res = someFunction(s, i);

  foreach(var r in res) {
      if(!r.Passed) return null;
  }

  // Rest of code...

  return ret;
}

我意识到这个例子有点做作，但我很想把foreach循环重构成一个LINQ语句，然后将其视为一个保护子句。同样，在一个人为的例子中，代码的意图并不明显，someFunction()可能会有一些其他副作用，或者结果可能会在代码的// Rest中使用....

if (string.IsNullOrEmpty(s) || i == null) return null;
if (someFunction(s, i).Any(r => !r.Passed)) return null;

给出以下重构函数:

void string fooBar(string s, int? i) {

  if (string.IsNullOrEmpty(s) || i == null) return null;
  if (someFunction(s, i).Any(r => !r.Passed)) return null;

  // Rest of code...

  return ret;
}

我想说的是，你应该有尽可能多的需要，或者任何使代码更干净的(如保护子句)。

我个人从来没有听过/见过任何“最佳实践”说你应该只有一个返回语句。

在大多数情况下，我倾向于根据逻辑路径尽快退出函数(保护子句就是一个很好的例子)。

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。

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?

是的，有:

The single exit point gives an excellent place to assert your post-conditions. Being able to put a debugger breakpoint on the one return at the end of the function is often useful. Fewer returns means less complexity. Linear code is generally simpler to understand. If trying to simplify a function to a single return causes complexity, then that's incentive to refactor to smaller, more general, easier-to-understand functions. If you're in a language without destructors or if you don't use RAII, then a single return reduces the number of places you have to clean up. Some languages require a single exit point (e.g., Pascal and Eiffel).

这个问题通常被提出为多个返回或深度嵌套的if语句之间的错误二分法。几乎总有第三种解决方案，它是线性的(没有深度嵌套)，只有一个出口点。

更新:MISRA的指导方针显然也提倡单次退出。

需要澄清的是，我并不是说拥有多个回报总是错误的。但如果有其他等价的解决方案，有很多很好的理由选择单一回报的方案。

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。

拥有多个出口点本质上与使用GOTO是一样的。这是不是件坏事取决于你对迅猛龙的看法。