lua table addressing

Question

I have a table logTable = {["cdm"] = "log text", ["data_engine"] = "log text"}

The code:

for k,v in pairs(logTable) do
    print(v["cdm"]) end

Gives the desired result: log text

However

print(logTable["cdm"])

returns nothing. What am I doing wrong here?

EDIT:

So this is actually how I am making the table:

table.insert(logTable, { [probeName] = file.read('export/'..robotName..'/probes/'..probeGroup..'/'..probeName..'/'..probeName..'.log')})

Where probeName is a variable, could it be that I need to ["probeName"] to make it a string? However this takes it as a literal and not a variable?

How can I use a variable as table index/key

Your example code works fine. codepad.org/n8z78Bae There must be something different going on in your actual code? — user197131
– user197131, Commented Jul 6, 2012 at 9:19
So this is actually how I am making the table: table.insert(logTable, { [probeName] = file.read('export/'..robotName..'/probes/'..probeGroup..'/'..probeName..'/'..probeName..'.log')}) Where probeName is a variable, could it be that I need to ["probeName"] to make it a string? However this takes it as a literal and not a variable? How can I use a variable as table index/key — Teknetik
– Teknetik, Commented Jul 6, 2012 at 9:24

Ilmo Euro · Accepted Answer · 2012-07-06 09:59:49Z

2

You actually have a table inside a table here, so your table looks like this:

{
    { 
      ["cdm"] = "log text",
      ["data engine"] = "log text"
    }
}

That's why your print(logTable["cdm"]) doesn't work. table.insert is also meant to be used with number-indexed tables; this time, the dictionary syntax is clearer:

logTable["probeName"] = file.read('export/'..robotName..
                                  '/probes/'..probeGroup..'/'
                                  ..probeName..'/'..probeName..'.log')

answered Jul 6, 2012 at 9:59

Ilmo Euro

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1 Comment

Michal Kottman Over a year ago

In the latter case logTable["probeName"] can be also written as logTable.probeName. Unless you actually want to use the value of probeName variable, in which case you should use just logTable[probeName].

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