Better to have two variables to designate whether a variable exists, or one

Question

Lets say I have a string variable FirstName. FirstName can be null. I need to know if FirstName exists or not.

Is it better to just use one variable: FirstName and if FirstName is empty assume that it doesn't exists

OR

Create two variables:
Boolean HasFirstName and String FirstName

The benefits of this is I know positively that FirstName doesn't exist but on the down side it creates two variables.

Answer 1

I would argue against both choices and would use an option type instead. An option type either contains no value or, or in this case, a string.

Many languages, especially functional ones, have such types built-in. Even if your chosen language doesn't support it directly, an Option<T> is a simple type to create.