How to create an object metatable which is a number but it has member functions

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#1

I’m trying to make a stats table, however certain stat values themselves have member values.

For example

local stat = {}
stat.Speed = 10
stat.Speed.Stamina = 20
stat.Speed.Recovery = 3
stat.Health = 100
stat.Health.Healrate = 1

Such that

print(stat.Speed)

will print “10” and

print(stat.Speed.Stamine)

prints out “20”

I know metatable has the “.__call” method, but I want something where it returns, instead of the table, it returns the value assigned to it.

#2

b…but why wouldnt you just do something like this? It’s just more simple (in my eyes) :roll_eyes:

local stat = {}
stat.Speed = {}
stat.Speed.Speed = 10
stat.Speed.Stamina = 20
stat.Speed.Recovery = 3
#3

Because it feels redundant to call “stat.Speed.Speed”. Additionally I want to replicate how something like vector3 not only when called returns a vector3 value but has methods attached to the objects as well.

With what you are suggesting, it’s like having to get a vector3 value by calling “vector3.vector3” instead of just saying “vector3”.

In my case when I call “stat.Speed” it returns “10”, but it also has member methods and values I can call.

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#4

You can do something like this to achieve the behavior you want.

local test = {}
test.speed = {}
test.speed.stamina = 20
test.speed.recovery = 3


setmetatable(test.speed, {
	__tostring = function() return 10 end,
	__mul = function(a, b) return tostring(a) * tostring(b) end,
	__div = function(a, b) return tostring(a) / tostring(b) end,
	__add = function(a, b) return tostring(a) + tostring(b) end,
	__sub = function(a, b) return tostring(a) - tostring(b) end,
})

print(5 + test.speed, 5 * test.speed, 5 / test.speed, 5 - test.speed)
-- outputs 15, 50, 0.5, -5

print(test.speed.stamina, test.speed.recovery)
--outputs 20, 3
#5

Why does “tostring” return a number value? Also with this doesn’t this mean I have to do something like “test.speed+0” to get the value of speed?

#6

Whenever you try to print out a table, it will try to invoke it’s __tostring method. If it exists, it will return whatever that function returns. If it does not, it will print out the table like normal.

By modifying that method, I can have it return a number and then use that method to modify the mathematical methods of the table in order to have it behave like a number, while still having the properties of a table.

There are probably better ways to go about this, but this is just a quick solution I found to the strange question that you asked.

And no, you do not have to do print(test.speed + 0) in order to retrieve the numerical value. You can simply do print(test.speed).

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