Fields and methods of metatable are not visible on table right after setmetatable

Question

This is Pico-8 lua. I have the following function, which fails at the marked assert. I do not understand how this can happen. I have used setmetatable on two other occasions and it is working there. I have no clue here.

function particle:new(o)
    setmetatable(o, self)
    assert(self.spd, "works")
    assert(getmetatable(o).spd, "works")
    assert(o.spd, "this fails") -- < this assert fails, the ones above succeed
    add(anims,o)
end

score 2 · Accepted Answer · answered Dec 12 '21 at 13:55

2

Looks like you forgot

self.__index = self

Without this o.spd will not refer to particle.spd, if o.spd is nil.

answered Dec 12 '21 at 13:55

Piglet

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Thanks so much. I still don't understand all this. – ziggystar Dec 12 '21 at 13:58
if there is something particular you don't understand you can always post a question here. – Piglet Dec 12 '21 at 14:00

Fields and methods of metatable are not visible on table right after setmetatable

1 Answers1