I think the parent comment was saying that you could always make that explicit. > By setting the value as null initially I can easily check whether the variabl

I think the parent comment was saying that you could always make that explicit. > By setting the value as null initially I can easily check whether the variable has been filled or not I don't think there's anything wrong with this but it does mean your variable can be in two states~, one where "it shows it should be filled" and one where the value is present and can be used. You can use null for this if you want and most programmers will understand these states. You can also choose to make this even more explicit by creating a type that expresses this. example in Kotlin but you get the idea (applies to any variable in any language) sealed class ThatVariableYouCareAbout { object ShouldBeFilled: ThatVariableYouCareAbout() data class HasBeenFilled(val x: String): ThatVariableYouCareAbout() } // usage fun test(thatVar: ThatVariableYouCareAbout) { if(thatVar is ShouldBeFilled) { // } else if(thatVar is HasBeenFilled) { } } Seems overly verbose but that's the reality of the variable you're talking about. This represents those states you described. `null` is a crutch in most languages for representing this state and the cause of a lot of subtle bugs (people use it to reset/clear out values too which in reality could represent a different state depending on what you _really_ want the variable to represent). All that being said, null is generally understood to have this meaning~ and I have/do use it but with an understanding that it's of lazyness/not wanting to be overly verbose (language consideration). The case you are describing is very familiar to me (rendering UI with initial states through a framework like react) and having an explicit type for the initial state is the ideal, or at least the most explicit, solution. Option works for 2-state variables like this