try and catch approach

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Hi I have a simple question and would be nice if someone could answer.

How much is it a good idea for example when I am writing a class say

CSomeClass

that I make it's methods throw exceptions.

Than on the other hand, whoever may have to use this class, should put the
code where CSomeclass is used, in

try{}

block.

e.g., place where CSomeclass is being used

C++

try
{
CSomeclass b;
b.f1();
...

}
catch (CSomeclass exception)
{

}

thanks.

or should I make the functions just return error values instead?

Posted 31-Oct-12 1:03am

WebMaster

Updated 31-Oct-12 1:06am

v2

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3 solutions

Solution 3

There are no definitive answers, but here are some things to keep in mind:

* If an error is expected and can be easily handled, this is better done in a return code.

* If an error occurs in a constructor, it should throw, as there is no way of returning an error code. Old-style C++ coding practice was to have a two-stage construction, where you first construct and then call a separate Create function to be able to get an error code. This style is now discouraged, and exceptions are the recommended way of handling errors in construction.

* Your code is not the only one that can throw exceptions. If any functions or libraries your code calls can throw exceptions, the user of your class will have to try to catch exceptions at some level.

* You have been given some .NET references in comments and answers. If you are not using managed C++ (e.g. in .NET), you should consider that exceptions are exit points from functions, so that any resource that needs to be freed (dynamically allocated memory, file handles, semaphores etc) before an exit should be kept in a RAII-type container, like auto_ptr, shared_ptr etc.

Posted 31-Oct-12 2:48am

Orjan Westin

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E.F. Nijboer · Accepted Answer · 2012-10-31T01:18:00

Solution 1

If you catch the exception, can you fix it in such a way that the function will return like normal without the calling code having to know about it, than yes. But if you cannot do anything useful to resolve the situation, what is the value of caching the exception?

Also, have a look here:
Exception Handling Best Practices in .NET[^]

Good luck!

Posted 31-Oct-12 1:18am

E.F. Nijboer

Comments

Orjan Westin 31-Oct-12 8:51am

Standard C++ have slightly different exception concerns than Managed C++/.NET does, in particular when it comes to resource management.

MT_ · Accepted Answer · 2012-10-31T01:19:00

This can not be answered in one line as it is generally based on circumstances of how the class is being used and sometimes on the architecture's personal view-point.

I would personally think if it is in same layer you may throw it but in case if it going across layer boundary i.e. from data layer to business layer or from business layer to UI layer (in standard 3-tier architecture), then its better to handle it in the class and then return appropriate error message.

As I said, this is a debatable topic, and if you search on Google for "throwing vs catching exception" it will return you good amount of reading material.

Hope that helps or atleast provides some direction.

Thanks
Milind