CODEWITHSUNDEEP
functionluaargumentslua-table
SGali
SGali

Reputation: 70

Passing a table as argument to function in Lua

I want to loop through different indexed tables by only passing the initial table as an argument. I currently have this table:

local table = {
stuff_1 = {
    categories = {},
    [1] = { 
        name = 'wui',
        time = 300
    }
},
stuff_2 = {
    categories = {'stuff_10', 'stuff_11', 'stuff_12'},
    stuff_10 = {
        categories = {},
        [1] = {
            name = 'peo',
            time = 150
        },
        [2] = { 
            name = 'uik',
            time = 15
        },
        [3] = { 
            name = 'kpk',
            time = 1230
        },  
        [4] = {     
            name = 'aer',
            time = 5000
        }
    },
    stuff_11 = {
        categories = {},
        [1] = { 
            name = 'juio',
            time = 600
        }
    },
    stuff_12 = {
        categories = {},
        [1] = {
            name = 'erq',
            time = 980
        },
        [2] = {
            name = 'faf',
            time = 8170
        }
    }
}

I wanted to make a recursive function to check if the name in any of those tables was equal to some certain thing and return a string. The recursivity lies in the idea of updating this table with whatever ammount I'd like (or until a certain limit). I don't understand exactly what's wrong since when I try:

for k, v in pairs(table) do
    print(k, v, #v.categories)
end

It correctly prints:

stuff_2 table: 0x10abb0 3
stuff_1 table: 0x10aab8 0

But when passing the table as a parameter to the the function below, it gives this error:

[string "stdin"]:84: attempt to get length of field 'categories' (a nil value)

Function:

function checkMessage(table)
    local i = 1
    local message = ""

    for k, v in pairs(table) do 
        if(#v.categories == 0) then  
            while(v[i]) do 
                if(v[i].name == 'opd') then 
                    if(v[i].time ~= 0) then 
                        message = "return_1"
                    else 
                        message = "return_2"
                    end 
                end 
                i = i + 1 
            end
        else
            checkMessage(table[k])
        end 
    end 
    return message 
end

EDIT: The problem lies in not ignoring that when using pairs onto the table, this doesn't just have tables with a category subtable but it also has a table named category, if this is ignored then the problem is fixed.

Upvotes: 3

Views: 13930

Answers (1)

Mud
Mud

Reputation: 29021

You're recursing into subtables that don't have a categories field. Trying to access categories on them yields nil, which you then try to use the length operator on. Hence your error:

  attempt to get length of field 'categories' (a nil value)

If you can't hand trace your app, put in more print statements or get a line level debugger.

Upvotes: 4

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