Question

I have this method to find an object in a list in C++.

Step Config::getStep(string stepName)
{
    for(int i=0; i<_NoSteps; i++)
    {
        if(_Steps[i].getStepNameStr().compare(stepName)==0)
        {
            return _Steps[i];
        }
    }

    cout << "ERROR. No processing step found for: " << stepName << endl;
    // case 1: throw exception
    // case 2: return null
}

I got an error while compiling: ‘not all control paths return a value’ as I set it ‘treated warning as error’

I would like to know how to:

1. how to throw a custom exception if there is no object found

2. how to return a NULL object in C# like: return null

Thanks in advance.

Answer 1

You can either return a pointer to an object, or a reference. In C++, unlike C#, you return the object by value, therefore, the object gets copied. To return it by reference, write Step& Config::getStep(string stepName).

To throw an exception, just write throw MissingStepException(); and then handle it like this:

try {
    Step s = c.getStep("step");
}
catch (MissingStepException& ex) {
    // handle
}

You need to define MissingStepException class first, of course.

Choosing what to do in general: return NULL or throw exception depends on your logic: if missing step is a logic error or an unlikely condition, it’s better to use exception, otherwise returning a NULL pointer would do.