我通常的策略是在函数的末尾只有一个return语句，除非通过添加更多的return语句来大大降低代码的复杂性。事实上，我是Eiffel的粉丝，它通过没有return语句强制执行唯一的返回规则(只有一个自动创建的'result'变量来放入结果)。

当然，在某些情况下，有多个返回值的代码比没有返回值的代码更清晰。有人可能会说，如果一个函数太复杂，没有多个return语句就无法理解，那么就需要更多的返工，但有时对这种事情采取务实的态度是好的。

I always avoid multiple return statements. Even in small functions. Small functions can become larger, and tracking the multiple return paths makes it harder (to my small mind) to keep track of what is going on. A single return also makes debugging easier. I've seen people post that the only alternative to multiple return statements is a messy arrow of nested IF statements 10 levels deep. While I certain agree that such coding does occur, it isn't the only option. I wouldn't make the choice between a multiple return statements and a nest of IFs, I'd refactor it so you'd eliminate both. And that is how I code. The following code eliminates both issues and, in my mind, is very easy to read:

public string GetResult()
{
    string rv = null;
    bool okay = false;

    okay = PerformTest(1);

    if (okay)
    {
        okay = PerformTest(2);
    }

    if (okay)
    {
        okay = PerformTest(3);
    }

    if (okay)
    {
        okay = PerformTest(4);
    };

    if (okay)
    {
        okay = PerformTest(5);
    }

    if (okay)
    {
        rv = "All Tests Passed";
    }

    return rv;
}

作为嵌套if的替代方法，有一种使用do/while(false)在任何地方爆发的方法:

    function()
    {
        HRESULT error = S_OK;

        do
        {
            if(!SUCCEEDED(Operation1()))
            {
                error = OPERATION1FAILED;
                break;
            }

            if(!SUCCEEDED(Operation2()))
            {
                error = OPERATION2FAILED;
                break;
            }

            if(!SUCCEEDED(Operation3()))
            {
                error = OPERATION3FAILED;
                break;
            }
            if(!SUCCEEDED(Operation4()))
            {
                error = OPERATION4FAILED;
                break;
            }
        } while (false);

        return error;
    }

这为您提供了一个出口点，允许您进行其他嵌套操作，但仍然不是真正的深层结构。如果你不喜欢成功，你可以做任何失败的事情。这类事情还允许您在任意两个其他检查之间添加其他代码，而无需重新缩进任何内容。

如果你真的疯了，整个If块也可以宏化。: D

    #define BREAKIFFAILED(x,y) if (!SUCCEEDED((x))) { error = (Y); break; }

    do
    {
        BREAKIFFAILED(Operation1(), OPERATION1FAILED)
        BREAKIFFAILED(Operation2(), OPERATION2FAILED)
        BREAKIFFAILED(Operation3(), OPERATION3FAILED)
        BREAKIFFAILED(Operation4(), OPERATION4FAILED)
    } while (false);

我能想到的一个很好的理由是代码维护:您有一个单一的退出点。如果你想改变结果的格式，…，它的实现要简单得多。此外，为了调试，你可以在那里插入一个断点:)

话虽如此，我曾经不得不在一个库中工作，那里的编码标准强制要求“每个函数一个返回语句”，我发现这相当困难。我写了很多数值计算代码，经常有“特殊情况”，所以代码最终很难跟上……

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。

有时出于性能考虑，这是必要的(我不想获取不同的缓存线，就像继续一样;有时)。

如果你不使用RAII分配资源(内存、文件描述符、锁等)，那么多次返回很容易出错，而且肯定是重复的，因为释放需要手动执行多次，你必须仔细跟踪。

在这个例子中:

function()
{
    HRESULT error = S_OK;

    if(SUCCEEDED(Operation1()))
    {
        if(SUCCEEDED(Operation2()))
        {
            if(SUCCEEDED(Operation3()))
            {
                if(SUCCEEDED(Operation4()))
                {
                }
                else
                {
                    error = OPERATION4FAILED;
                }
            }
            else
            {
                error = OPERATION3FAILED;
            }
        }
        else
        {
            error = OPERATION2FAILED;
        }
    }
    else
    {
        error = OPERATION1FAILED;
    }

    return error;
}

我会把它写成:

function() {
    HRESULT error = OPERATION1FAILED;//assume failure
    if(SUCCEEDED(Operation1())) {

        error = OPERATION2FAILED;//assume failure
        if(SUCCEEDED(Operation3())) {

            error = OPERATION3FAILED;//assume failure
            if(SUCCEEDED(Operation3())) {

                error = OPERATION4FAILED; //assume failure
                if(SUCCEEDED(Operation4())) {

                    error = S_OK;
                }
            }
        }
    }
    return error;
}

这当然看起来更好。

这在手动资源释放的情况下尤其有用，因为在哪里和哪些释放是必要的是相当直接的。如下例所示:

function() {
    HRESULT error = OPERATION1FAILED;//assume failure
    if(SUCCEEDED(Operation1())) {

        //allocate resource for op2;
        char* const p2 = new char[1024];
        error = OPERATION2FAILED;//assume failure
        if(SUCCEEDED(Operation2(p2))) {

            //allocate resource for op3;
            char* const p3 = new char[1024];
            error = OPERATION3FAILED;//assume failure
            if(SUCCEEDED(Operation3(p3))) {

                error = OPERATION4FAILED; //assume failure
                if(SUCCEEDED(Operation4(p2,p3))) {

                    error = S_OK;
                }
            }
            //free resource for op3;
            delete [] p3;
        }
        //free resource for op2;
        delete [] p2;
    }
    return error;
}

如果在没有RAII(忘记异常问题!)的情况下使用多个出口编写这段代码，则必须多次写入删除。如果你用}else{then 这有点难看。

但是RAII使得多个出口资源问题变得毫无意义。