Option | Unreal Editor for Fortnite Documentation

The option type can contain one value or can be empty.

In the following example, MaybeANumber is an optional integer ?int that contains no value. A new value for MaybeANumber is then set to 42.

var MaybeANumber : ?int = false # unset optional value
set MaybeANumber := option{42} # assigned the value 42

MaybeANumber : ?int = option{42} # initialized as 42

MaybeAnotherNumber : ?int = false # unset optional value

Creating an option: You can initialize an option with one of the following:

No value: Assign false to the option to mark it as unset.
Initial value: Use the keyword option followed by {}, and an expression between the {}. If the expression fails, the option will be unset and have the value false.

Specify the type by adding ? before the type of value expected to be stored in the option. For example ?int.

if (Number := MaybeANumber?):
    Number # if MaybeANumber is not empty, then its value is stored in Number for you to use.

Accessing an element in an option: Use the query operator ? with the option, such as MaybeANumber?. Accessing the value stored in an option is a failable expression because there might not be a value in the option, and so must be used in a failure context.

The following is an example of using an option type to save a reference to a spawned player and, when a player is spawned, to have the trigger device react:

my_device := class<concrete>(creative_device):
    var SavedPlayer : ?player = false # unset optional value
 
    @editable
    PlayerSpawn : player_spawner_device = player_spawner_device{}
 
    @editable
    Trigger : trigger_device = trigger_device{}
 
    OnBegin<override>() : void =
        PlayerSpawn.PlayerSpawnedEvent.Subscribe(OnPlayerSpawned)
 
    OnPlayerSpawned(Player : player) : void =
        set SavedPlayer = option{Player}
        if (TriggerPlayer := SavedPlayer?): 
            Trigger.Trigger(TriggerPlayer)

Persistable Type

An option is persistable if its value is persistable, which means that you can use them in your module-scoped weak_map variables and have their values persist across game sessions. For more details on persistence in Verse, check out Using Persistable Data in Verse.