🔎

    Optional Type (?)

    Optional Type🔗

    You can indicate that a value is not required.

    Just append ? to the type.

    /// If provided, it must be an int; otherwise it can be omitted
setting: int?

    Where ? Can Appear🔗

    While we say “append ? to the type”, strictly speaking you can place ? after a type name or after an array type.

    /// Either int? or [int]
/// Equivalent to writing int? | [int]?
setting: int? | [int]
    • Inside arrays
    /// This is an array of int?
/// In JSON, values like [null, 100] are allowed.
/// In languages without null like TOML, only an empty array can represent absence.
setting: [int?]
    • Not allowed
    /// This form is not allowed!
setting: int |?