Type casting and smart-casting

Type casting lets you check an entity’s type at runtime and safely access its fields.

The is and isnt operators

Use is to check whether an entity is of a given type:

if target is Asteroid {
  Pewpew:Print("It's an asteroid!")
}

if target isnt Ship {
  Pewpew:Print("It's not a ship!")
}

Smart-casting

Smart-casting allows you to check and cast a custom entity in one step using if let. Once cast, all fields and methods of that entity type are available within the block:

entity ShieldPowerUp {
  fixed strength

  spawn(fixed strength) {
    self.strength = strength
  }
}

fn OnCollision(entity collided) {
  if let targetEntity = collided is ShieldPowerUp {
    targetEntity.strength = 100fx
    Pewpew:Print("Shield boosted!")
  }
}

Smart-casting works in regular if conditions and in match statements as well. The cast variable is scoped to the block where the check succeeds.