Module and callbacks

Back to Lua 5.4.

Return one behavior table. Every member is optional; Rustic looks up a callback before calling it. Returning no value is also accepted and creates a no-op behavior.

local speed = 4.0 -- private state for this behavior instance

return {
  Start = function()
    rustic.log("info", "started " .. rustic.entity_id())
  end,

  OnEnable = function() end,

  FixedUpdate = function(dt)
    local key = rustic.key("KeyW")
    if key.held then
      local x, y, z = rustic.get_translation()
      rustic.set_translation(x, y, z + speed * dt)
    end
  end,

  Update = function(dt) end,
  OnDisable = function() end,
  OnDestroy = function() end,
}

Canonical public names are Start, FixedUpdate, Update, OnEnable, OnDisable, OnDestroy, OnCreate, and OnStop. The legacy spellings on_start, fixed_update, update, on_enable, on_disable, and on_destroy still work. on_create and on_stop are compatible spellings of OnCreate and OnStop. Stop is not a callback; use OnStop for teardown before owner cleanup. If both canonical and legacy names are present, the canonical callback wins. Use FixedUpdate(dt) for physics and deterministic movement; use Update(dt) for frame-rate work. OnStart is not a Lua callback name. A script with OnStart can load successfully while its startup function never runs; rename it to Start.

The engine-wide callback model also defines OnCollisionEnter, OnCollisionStay, and OnCollisionExit. The current embedded Lua adapter does not yet bind those three names, so do not rely on them in Lua code in this release.