图案以避免嵌套的try catch块？ [英] Pattern to avoid nested try catch blocks?

问题描述

考虑一个情况我有执行计算的三个（或更多）的方式，每一个都可以失败，一个例外。为了尝试每一次计算，直到我们找到一个成功，我一直在做以下内容：

Consider a situation where I have three (or more) ways of performing a calculation, each of which can fail with an exception. In order to attempt each calculation until we find one that succeeds, I have been doing the following:

double val;

try { val = calc1(); }
catch (Calc1Exception e1)
{ 
    try { val = calc2(); }
    catch (Calc2Exception e2)
    {
        try { val = calc3(); }
        catch (Calc3Exception e3)
        {
            throw new NoCalcsWorkedException();
        }
    }
}

有没有公认的格局其中实现这一目标的一个更好的方式？当然，我可以包中失败则返回空一个辅助方法每次计算，然后只用 ?? 运营商，但有没有这样做更普遍的一种方式（即无需写我想用每一种方法）一个辅助方法？我想过写使用泛型它包装在一个try / catch任何给定的方法，失败时返回null一个静态方法，但我不知道我怎么会去这一点。任何想法？

Is there any accepted pattern which achieves this in a nicer way? Of course I could wrap each calculation in a helper method which returns null on failure, and then just use the ?? operator, but is there a way of doing this more generally (i.e. without having to write a helper method for each method I want to use)? I've thought about writing a static method using generics which wraps any given method in a try/catch and returns null on failure, but I'm not sure how I would go about this. Any ideas?

推荐答案

尽量不要使用控制流或平常的情况例外。

As far as possible, don't use exceptions for control flow or unexceptional circumstances.

但直接回答你的问题（假设所有的异常类型相同）：

But to answer your question directly (assuming all the exception-types are the same):

Func<double>[] calcs = { calc1, calc2, calc3 };

foreach(var calc in calcs)
{
   try { return calc(); }
   catch (CalcException){  }
} 

throw new NoCalcsWorkedException();

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