CODEWITHSUNDEEP
debugginglualua-table
creyD
creyD

Reputation: 2126

How to get data from a Lua table except nil

I'm trying to recieve data from a pretty big table (bigTable) and the getRow function should rearrange some data for faster calculation (specific information below). The problem is that some of this values don't exist (-->are nil). I thought I'd taken care of this by adding the if-Statement to check first if the value does even exist, but I still get the error below. Thanks for your help.

My function (from line 46):

function getRow(a, b)
    row = {}
    for d = 0, 3 do
        if (bigTable[a + d][b + d]) then
            table.insert(row, bigTable[a + d][b + d])
        end
    end
    return row
end

Error:

C:\Program Files (x86)\Lua\5.1\lua.exe: .\solution_11.lua:49: attempt to index field '?' (a nil value)
stack traceback:
        .\solution_11.lua:49: in function 'getRow'
        .\solution_11.lua:69: in function 'diagonal'
        .\solution_11.lua:89: in main chunk
        [C]: ?

The getRow()-function should get the values of the two dimensional array from point A, B "diagonally" downwards.

Upvotes: 1

Views: 282

Answers (1)

Mike V.
Mike V.

Reputation: 2215

The goal can be achieved by exchanging this line

if (bigTable[a + d][b + d]) then

with this line

if a and b and type(bigTable[a + d])=='table' and bigTable[a + d][b + d] then

This solves the problem because every possibility is checked (a or b can't be nil, the table you trying to access is even existent and it contains the value you trying to access). You only checked for the last one and therefore you got an error when the value was nil.

Upvotes: 1

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