Question

Should I validate input parameters on all functions I create? Input isn’t passed from a user, but from other routines as part of an automatic process.

I use error handling. I’m not sure what more validating input could do for me. If the input isn’t valid, that’s pretty much the same thing as an error, isn’t it?

Answer 1

A lot will depend on how public your function is and how destructive bad input will be to your application/data-store.

If there is a tight coupling between the code calling the function and the function itself I think validation is overkill and will only add complexity to your solution.

However, if your code is, for example, part of a library used by more than just you/your code add as much validation as needed. You don’t want it to be your code that fails/allows something wrong to happen because you didn’t validate the input.

Think of libraries/functions you already use. If you chuck bad values at them, how do they respond? Do they respond with a tailored error (e.g “Elephant” is not a fruit) or an internal error which is a by-product of your bad input (e.g “Object reference not set to an instance of an object”)?