[英]Design Pattern for Error Handling
I've ran into this problem a few times on various projects, and I've wondered if there's a better solution than the one I normally end up using. 我在各个项目中遇到过这个问题几次,我想知道是否有比我通常最终使用的解决方案更好的解决方案。
Say we have a series of methods that need to execute, and we want to know if something goes wrong within one of the methods and break out gracefully (potentially undo-ing any previous changes...), I typically do the following (pseudo C# because it's what I'm most familiar with): 假设我们有一系列需要执行的方法,并且我们想知道其中一个方法中是否出现问题并优雅地突破(可能撤消任何先前的更改......),我通常会执行以下操作(伪C#,因为这是我最熟悉的):
private bool SomeMethod()
{
bool success = true;
string errorMessage = null;
success = TestPartA(ref errorMessage);
if (success)
{
success = TestPartB(ref errorMessage);
}
if (success)
{
success = TestPartC(ref errorMessage);
}
if (success)
{
success = TestPartD(ref errorMessage);
}
//... some further tests: display the error message somehow, then:
return success;
}
private bool TestPartA(ref string errorMessage)
{
// Do some testing...
if (somethingBadHappens)
{
errorMessage = "The error that happens";
return false;
}
return true;
}
I just wondered (and this is my question) if there's a better methodology for coping with this kind of thing. 我只是想知道(这是我的问题),如果有更好的方法来应对这种事情。 I seem to end up writing a lot of
if
statements for something that seems like it should be slicker. 我似乎最终写了很多
if
语句似乎应该更流畅。
I've been suggested having a loop over a set of delegate functions, but I'd be worried that would be over-engineering the solution, unless there's a clean way to do it. 我被建议在一组委托函数上进行循环,但是我担心这会过度设计解决方案,除非有一个干净的方法来完成它。
I think you should probably be using exceptions. 我认为你应该使用例外。 Note you should generally only be catching exceptions at the "top level" in your application.
请注意,通常只应在应用程序的“顶层”捕获异常。
private void TopLevelMethod()
{
try
{
SomeMethod();
}
catch (Exception ex)
{
// Log/report exception/display to user etc.
}
}
private void SomeMethod()
{
TestPartA();
TestPartB();
TestPartC();
TestPartD();
}
private void TestPartA()
{
// Do some testing...
try
{
if (somethingBadHappens)
{
throw new Exception("The error that happens");
}
}
catch (Exception)
{
// Cleanup here. If no cleanup is possible,
// do not catch the exception here, i.e.,
// try...catch would not be necessary in this method.
// Re-throw the original exception.
throw;
}
}
private void TestPartB()
{
// No need for try...catch because we can't do any cleanup for this method.
if (somethingBadHappens)
{
throw new Exception("The error that happens");
}
}
I have used the built-in System.Exception class in my example; 我在我的例子中使用了内置的System.Exception类; you can create your own derived exception classes, or use the built-in ones derived from System.Exception.
您可以创建自己的派生异常类,也可以使用从System.Exception派生的内置类。
You could perhaps try looking at the "Open/Closed" section of the SOLID Principle. 您也许可以尝试查看SOLID原则的“打开/关闭”部分。 In your example you could perhaps create an
ITestRule
interface which contains a method called CheckRule()
that will updated your message and return a bool
. 在您的示例中,您可以创建一个
ITestRule
接口,其中包含一个名为CheckRule()
的方法,该方法将更新您的消息并返回一个bool
。 You would then create an interface implementation for each rule you want to test, and add that class to a List<ITestRule>
object. 然后,您将为要测试的每个规则创建一个接口实现,并将该类添加到
List<ITestRule>
对象。 From the Redmondo example above, I would change to the following: 从上面的Redmondo示例中,我将更改为以下内容:
var discountRules =
new List<ITestRule>
{
new TestPartA(),
new TestPartB(),
new TestPartC(),
new TestPartD(),
};
You would then pass the new List<ITestRule>
to an evaluator which will loop through each of the classes and runs the CheckRule()
method. 然后,您将新的
List<ITestRule>
传递给一个求值器,它将循环遍历每个类并运行CheckRule()
方法。
I try to stick to a principle known as 'Fail Fast'; 我试图坚持一个称为“快速失败”的原则; methods should fail when they are supposed to, and return immediately with details of the error.
方法应该在它们应该发生时失败,并立即返回错误的详细信息。 The calling method then responds appropriately (re-throw the exception to its caller, log the details, show an error if it's a UI-bound method, etc): -
然后调用方法适当地响应(将异常重新抛出给它的调用者,记录细节,如果它是一个UI绑定方法则显示错误等): -
http://en.wikipedia.org/wiki/Fail-fast http://en.wikipedia.org/wiki/Fail-fast
However, this does not mean using exceptions to control the flow of your application. 但是,这并不意味着使用异常来控制应用程序的流程。 Just raising an exception when you could deal with it is generally bad practice: -
刚养的时候,你可以对付它通常是不好的做法异常: -
http://msdn.microsoft.com/en-us/library/dd264997.aspx http://msdn.microsoft.com/en-us/library/dd264997.aspx
In your case, I'd re-write your code as (for example): - 在你的情况下,我会重新编写你的代码(例如): -
private bool SomeMethod()
{
bool success = false;
try
{
TestPartA();
TestPartB();
TestPartC();
TestPartD();
success = true;
}
catch (Exception ex)
{
LogError(ex.Message);
}
//... some further tests: display the error message somehow, then:
return success;
}
private void TestPartA()
{
// Do some testing...
if (somethingBadHappens)
{
throw new ApplicationException("The error that happens");
}
}
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