Casts

Use the as operator for explicit casts: expression as TargetType. Only certain conversions are allowed (see below); invalid combinations are rejected by the compiler.

Casting objects

Object references can only be cast to another script/object type when the types are related by inheritance (parent/child in the hierarchy).

Casting from a parent type to a child type may fail at runtime: if the value is not actually an instance of that child, the result is none. It's recommended to check for none after a narrowing cast.

Syntax: value as DerivedType.

script MyScript : ObjectReference {

    event onActivate(obj: ObjectReference) {
        // Narrow ObjectReference to Actor; may be none if obj is not an Actor
        var who: Actor = obj as Actor
        if who == none {
            return
        }
        // use who as Actor
    }
}

Casting to String and Bool

Many types can be cast explicitly to String. That's useful for debugging or if you want to show a message or notification to the user.

You can also cast suitable values to Bool when you want a boolean for if / while conditions (or to pass into something that expects Bool).

script MyScript {

    fun print(nums: [Int]) {
        Debug.Trace(nums as String)
    }

    fun bar(item: Form) {
        var isWeapon = (item as Weapon) as Bool
        if isWeapon {
            // do something
        }
    }
}

At runtime, none converts to false when cast to Bool. So in the example, if item as Weapon fails (none because it is not a weapon), (item as Weapon) as Bool is false. Only a non-none reference becomes true.

Coercing to Bool is one way to branch when you only care about success vs failure without comparing to none explicitly.

Implicit casts

There are several cases where the compiler will insert an implicit cast for you.

An expression of type Int can be promoted to Float in contexts where a Float is expected. For example, 1 + 1.0 has type Float.

Another case is objects related by inheritance. The compiler applies automatic upcast in comparison operators:

script MyScript : ObjectReference {

    event onActivate(obj: ObjectReference) {
        var player: Actor = Game.GetPlayer()
        // no explicit cast required here
        if obj != player {
            return
        }
    }
}