这是干净的代码吗？

Question

#include <fstream>
#include <iostream>
#include <stdexcept>
using namespace std;

class FileNotFound: public logic_error
{
public:
    explicit FileNotFound(const string& _Message):logic_error(_Message){}
};
int main()
{
    try
    {
        ifstream file;
        file.open("NoExistingFile");
        if (file.fail())
            throw FileNotFound("");
    }
    catch(const FileNotFound &e)
    {
        cout << "FileNotFound" << e.what();
    }
    catch(const exception &e)
    {
        cout << e.what();
    }

    return 0;
}

Output: FileNotFound

Is it Clean code (Robert Martin)? std::exception not provide "location of an error". Clean Code A Handbook of Agile Software Craftsmanship (Robert Martin) -> Chapter 7: Error Handling -> Provide Context with Exceptions

Answer 1

Considering the quoted paragraph, it is certainly not clean, because you just get the information of what happened, but you do not get the information from where the exception was thrown, therefore you can not trace it back for debugging.

Instead of using standard exceptions, I would advise to use boost exceptions , since they can provide the context from where the exception is thrown.

Answer 2

The more fundamental question is: Why use an exception in the first place? If it's a non-exceptional behavior (if it can be expected that a file might not be present), than no exception should be thrown at all. Instead control should flow along an "official path".

Answer 3

Add-on: It is not clean in the sense of the quoted book section (because the context needed to locate the problem is not provided with the exception -as others have mentioned) but also because:

1. The custom exception is used to manipulate control flow.

So instead of :

  throw FileNotFound(""); } catch(const FileNotFound &e) { 

Do only:

    cout << "FileNotFound" << e.what(); 

2. The variable name 'e' is not really self explanatory and should also not be repeated.

3. The exception class should have its own file.

4. You should not use error and exception interchangably (in your question). This is an extra tipp imho.