Factorio Forums

Posted: **Sun Oct 05, 2025 2:59 pm**

I'm starting to build an event with lots filter case

To summarise to look like this:

script.on_event(defines.events.on_built_entity, function(event) 
  game.print(serpent.block(event))
end, {
  {filter="type", type="constant-combinator"},
  {filter="ghost_type", ghost_type="constant-combinator"},
  {filter="type", type="train-stop"},
  {filter="ghost_type", ghost_type="train-stop"},
  {filter="rail"},
  {filter="rail-signal"}
})

Some filter are easy to reproduce in the event function, others are not

I would suggest that the event parameter contain a field that give filter results,
it would be a 1-1 map of filters with 2 possible values: true, false
if factorio does minimal evaluation for filters, it can have a nil value if the filter has not been evaluated

here it could give a result like

Code: Select all

{
  consumed_items = "[LuaInventory: temp]",
  entity = "[LuaEntity: train-stop at [gps=157.0,1.0]]",
  name = 6,
  player_index = 1,
  tick = 214527,
  filter_result={
    false,
    false,
    true,
    nil,
    nil,
    nil,
  }
}

which mean it's a train stop

This mean that really big events could use the results of the filters to route to smaller events without reevaluating every filters manually

Posted: **Sun Oct 05, 2025 3:10 pm**

Also before I was just putting a simple example, but actually I'm trying to make something that would permit to register and dispatch micro events like:

Code: Select all

player_built_entity.register({
  {filter="type", type="constant-combinator"},
  {filter="ghost_type", ghost_type="constant-combinator"}
}, function(event) game.print("You built a constant combinator") end)
player_built_entity.register({
  {filter="type", type="train-stop"},
  {filter="ghost_type", ghost_type="train-stop"}
}, function(event)  game.print("You built a train stop") end)
player_built_entity.register({{filter="rail"}}, function(event)  game.print("You built a rail") end)
player_built_entity.register({{filter="rail-signal"}}, function(event)  game.print("You built a rail signal") end)

the fact is for now I need to reevaluate filters manually

Finally this is not just for the on_build_entity event but for any event with filter

Factorio Forums

Getting event filter results

Getting event filter results

Re: Getting event filter results