Lua - Execute a Function Stored in a Table

Question

I was able to store functions into a table. But now I have no idea of how to invoke them. The final table will have about 100 calls, so if possible, I'd like to invoke them as if in a foreach loop. Thanks!

Here is how the table was defined:

game_level_hints = game_level_hints or {}
game_level_hints.levels = {}
game_level_hints.levels["level0"] = function()
    return
    {
        [on_scene("scene0")] =
        {
            talk("hint0"),
            talk("hint1"),
            talk("hint2")
        },
        [on_scene("scene1")] =
        {
            talk("hint0"),
            talk("hint1"),
            talk("hint2")
        }
    }
end

Aaand the function definitions:

function on_scene(sceneId)
    -- some code
    return sceneId
end

function talk(areaId)
    -- some code
    return areaId
end

EDIT:

I modified the functions so they'll have a little more context. Basically, they return strings now. And what I was hoping to happen is that at then end of invoking the functions, I'll have a table (ideally the levels table) containing all these strings.

It's not clear how or what you want invoked in the loop. Perhaps you can explain and give pseudo-code. BTW—Lua doesn't have pointers. Functions are values of type `function` and can be used anywhere in expressions. — Tom Blodget, Jun 17 '13 at 02:12

Paul Kulchenko · Answer 1 · 2013-06-17T03:02:41.817

Short answer: to call a function (reference) stored in an array, you just add (parameters), as you'd normally do:

local function func(a,b,c) return a,b,c end
local a = {myfunc = func}
print(a.myfunc(3,4,5)) -- prints 3,4,5

In fact, you can simplify this to

local a = {myfunc = function(a,b,c) return a,b,c end}
print(a.myfunc(3,4,5)) -- prints 3,4,5

Long answer: You don't describe what your expected results are, but what you wrote is likely not to do what you expect it to do. Take this fragment:

game_level_hints.levels["level0"] = function()
    return
    {
        [on_scene("scene0")] =
        {
            talk("hint0"),
        }
    }
end

[This paragraph no longer applies after the question has been updated] You reference on_scene and talk functions, but you don't "store" those functions in the table (since you explicitly referenced them in your question, I presume the question is about these functions). You actually call these functions and store the values they return (they both return nil), so when this fragment is executed, you get "table index is nil" error as you are trying to store nil using nil as the index.

If you want to call the function you stored in game_level_hints.levels["level0"], you just do game_level_hints.levels["level0"]()

score 5 · Accepted Answer · answered Jun 17 '13 at 03:09

5

Using what you guys answered and commented, I was able to come up with the following code as a solution:

asd = game_level_hints.levels["level0"]()

Now, asd contains the area strings I need. Although ideally, I intended to be able to access the data like:

asd[1][1]

accessing it like:

asd["scene0"][1]

to retrieve the area data would suffice. I'll just have to work around the keys.

Thanks, guys.

answered Jun 17 '13 at 03:09

brain56

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You probably could do that with metatables, but it is also probably not worth the effort ;) – dualed Jun 17 '13 at 09:33

score 1 · Answer 3 · answered Jun 17 '13 at 02:12

It's not really clear what you're trying to do. Inside your anonymous function, you're returning a table that uses on_scene's return value as keys. But your on_scene doesn't return anything. Same thing for talk.

I'm going to assume that you wanted on_scene and talk to get called when invoking each levels in your game_level_hints table.

If so, this is how you can do it:

local maxlevel = 99
for i = 0, maxlevel do
  game_level_hints.levels["level" .. i] = function()
    on_scene("scene" .. i)
    talk("hint" .. i)
  end
end
-- ...
for levelname, levelfunc in pairs(game_level_hints.levels) do
  levelfunc()
end

Lua - Execute a Function Stored in a Table

3 Answers3

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