Question

I’m trying:

let mutable ncon : NCon = null

and getting:

Error   1   The type 'NCon' does not have 'null' as a proper value

where type is declard in this way

type NCon(settings : ISettings) = ...

I’m planning to use it as static property and init it later when user will finish the settings so what am I doing wrong? why can’t I init mutable type with null?

must I use option? so to make it to be None or Some instead?

Answer 1

You have to supply a AllowNullLiteral to your NCon-Type like this:

[<AllowNullLiteral>]
type NCon(settings : ISettings) = ...

This is because F# prevents you from using Null … not a bad idea IMHO

To your other questions:
Yes I would rather use an option – and I would consider using a ref-cell too – but this depends on what you want to do with it.