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Tip of the Day
Language: C++
Expertise: Intermediate
Jan 28, 2000



Building the Right Environment to Support AI, Machine Learning and Deep Learning

Rules of Thumb for Designing Exception Classes

When designing an exception class, think of it as a standalone class with data members and member functions. A well-designed exception class should have a member function that returns a verbal description of the exception. In applications that use error codes, you should also include a member function that returns the exception's numeric code. This way, the handler of that exception doesn't need to look for this information elsewhere; it can retrieve it from the exception object directly.

  class myException
  // ..stuff
    const char * description() const;
    int code_number() const;

  catch( myException & ex)
    cout<<" error occurred: "<< ex.description();
    cout<< "with code: " << ex.code_number(); 

Remember also that sometimes the same exception can be thrown in similar but not identical situations. For example, a DBMS system can throw the same exception when it encounters a referential integrity problem or an attempt to insert a duplicate key. To distinguish between these errors, the handler can query the exception object and obtain a precise description of the actual error that occurred.

Danny Kalev
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