Programming against an enum in a switch statement, is this your way to do?

Question

Look at the code snippet:

This is what I normally do when coding against an enum. I have a default escape with an InvalidOperationException (I do not use ArgumentExc

Answer 1

This is probably going off topic, but maybe not. The reason the check has to be there is in case the design evolves and you have to add a new state to the enum.

So maybe you shouldn't be working this way in the first place. How about:

interface IDrivingState
{
    void Do();
}

Store the current state (an object that implements IDrivingState) in a variable, and then execute it like this:

drivingState.Do();

Presumably you'd have some way for a state to transition to another state - perhaps Do would return the new state.

Now you can extend the design without invalidating all your existing code quite so much.

Update in response to comment:

With the use of enum/switch, when you add a new enum value, you now need to find each place in your code where that enum value is not yet handled. The compiler doesn't know how to help with that. There is still a "contract" between various parts of the code, but it is implicit and impossible for the compiler to check.

The advantage of the polymorphic approach is that design changes will initially cause compiler errors. Compiler errors are good! The compiler effectively gives you a checklist of places in the code you need to modify to cope with the design change. By designing your code that way, you gain the assistence of a powerful "search engine" that is able to understand your code and help you evolve it by finding problems at compile-time, instead of leaving the problems until runtime.