Lua deleting an item from table (CoronaSDK)

Question

Been trying to work this out for hours and not getting anywhere despite lots of searching, so if somebody can help that would be great

My issue is I have a table of objects which are added like this

enemies[enemy_id] = enemy

Now when there is a collision at the end of the map I want to remove that enemy from the table. I have tried removing by

enemies[enemy_id] = nil

But when it gets to the last enemy the table is already empty for some reason. Say there's 3 enemies in a table, I print the count of the table. The first one is removed it shows 2 left, 2nd is removed it shows 0 left. Doesn't make sense

So how do you remove an item from a table? I have also tried table.remove but I need to key the same keys because they are the id of the enemy. I can post an example if need be

Don't use #t on sparse tables (when indices have gaps), it returns wrong result. — Egor Skriptunoff
@Luke not sure what you mean by "... I need to key the same keys". — greatwolf

dualed dualed · Accepted Answer · 2013-07-12T21:09:01

When working with "sparse keys" in Lua tables this pattern usually pays off for me:

-- add item to registry
registry[object] = key
registry[key] = object

-- iterate over all items in registry
for k,v in pairs(registry) do 
  if type(k) == "number" then do_something(k,v) end
end

-- remove item with key K from registry:
registry[registry[K]] = nil
registry[K] = nil

-- remove item O from registry:
registry[registry[O]] = nil
registry[O] = nil

Lua deleting an item from table (CoronaSDK)

2 Answers