others-how to solve the `loop in gettable` error in lua?

1. Problem

In this post , I will demo how to solve loop in gettable error when using lua.

Here is the error detail:

/usr/local/bin/lua: ...ects/bswen-demo/src/debug/test_object_create.lua:14: loop in gettable
stack traceback:
    ...ects/bswen-demo/src/debug/test_object_create.lua:14: in function 'test1'
    ...ects/bswen-demo/src/debug/test_object_create.lua:36: in main chunk
    [C]: ?

the code that caused the problem:

The class in test_object.lua:

local function init()
    local obj = {
        root = {},
        options = {noreduce = {}}
    }

    obj._stack = {obj.root, n=1}
    return obj
end

local _M = init()

function _M:new()
    local obj = init()

    obj.__index = self
    setmetatable(obj, self)

    return obj
end

function _M:text(text)

end

_M.cdata = _M.text
_M.__index = _M
return _M

Actually , you can use any type of lua class to test this problem.

The client:

local handler = require "test_object" -- import the class

local function test1()
    for i=1,200 do
        handler = handler:new() -- initialize the handler class
        handler:text("bbb"..tostring(i)) -- call the function of the class
    end
end

test1() -- call the test function

run the above code, we got this error:

/usr/local/bin/lua: ...ects/bswen-demo/src/debug/test_object_create.lua:14: loop in gettable
stack traceback:
    ...ects/bswen-demo/src/debug/test_object_create.lua:14: in function 'test1'
    ...ects/bswen-demo/src/debug/test_object_create.lua:36: in main chunk
    [C]: ?



2. Solution

change your client as follows:

local function test2()
    for i=1,200 do
        local handler_good2 = handler:new(i) -- the key point: define the variable using a new name.
        handler_good2:text("aa")
    end
end

reason: It seems that if you have 100 nested reference in lua, there will be ‘loop in gettable’ error at runtime.

After changing from

handler = handler:new()

to this:

local handler_good2 = handler:new(i)

we are trying to avoid the naming confliction or polution in the lua namespaces.



3. Summary

In this post, I demonstrated how to solve the ‘loop in gettable’ error when using lua. That’s it, thanks for your reading.

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