Convert array to string in LUA

Question

Trying to convert this to a string customLog2 = {} Which will really look like Log = { {Group = ID, Pos = Numbers}, {Group = ID, Pos = Numbers} } I tried this

local Data = string.format( "LogBook = %s ", customLog2 )

But Because CustomLog is an array and not a string or a number I cant insert it. Im trying to get the array into a string for this VariableFile:write(Data) So if anyone can help that would be awesome thanks.

So I want my Output to look like this "local Data = string.format( "LogBook = %s ", customLog2 )" so I can use :write then in my newly created file it should look like this Log = { {Group = ID, Pos = Numbers}, {Group = ID, Pos = Numbers} }

So this function works expect one thing.

function TableSerialization(t, i)
    local text = "{\n"
    local tab = ""
    for n = 1, i + 1 do                                                                 --controls the indent for the current text line
        tab = tab .. "\t"
    end
    for k,v in pairs(t) do
        if type(k) == "string" then
            text = text .. tab .. "['" .. k .. "'] = "
        else
            text = text .. tab .. "[" .. k .. "] = "
        end
        if type(v) == "string" then
            text = text .. "'" .. v .. "',\n"
        elseif type(v) == "number" then
            text = text .. v .. ",\n"
        elseif type(v) == "table" then
            text = text .. TableSerialization(v, i + 1)
        elseif type(v) == "boolean" then
            if v == true then
                text = text .. "true,\n"
            else
                text = text .. "false,\n"
            end
        elseif type(v) == "function" then
            text = text .. v .. ",\n"
        elseif v == nil then
            text = text .. "nil,\n"
        end
    end
    tab = ""
    for n = 1, i do                                                                     --indent for closing bracket is one less then previous text line
        tab = tab .. "\t"
    end
    if i == 0 then
        text = text .. tab .. "}\n"                                                     --the last bracket should not be followed by an comma
    else
        text = text .. tab .. "},\n"                                                    --all brackets with indent higher than 0 are followed by a comma
    end
    return text
end

My input array lets say looks like this Log = { Group = WestAPC } now this does not work because WestAPC is not a string but if WestAPC looks like this "WestAPC" it works. I need it to not be in string form.

{ Group = WestAPC } vs { Group = "WestAPC" } both construct a table with a single field with the same key, the string "Group". The value is set from the respective expression. In the second, the expression is a literal string. In the first, the expression is a variable. The variable's value might be nil, a string, or any other type of value. In a table, if a field value is set to nil, the key-value pair is removed from the table. So, what's your goal here? Perhaps the problem is in code that you haven't shown yet. — Tom Blodget
– Tom Blodget, Commented Jun 27, 2018 at 3:43

Gamora · Accepted Answer · 2020-03-05 14:28:09Z

5

To be clear, customLog is a table - that is, an associative array of key value pairs. Here’s an easy way to iterate over all key/value pairs and concatenate the pairs into one string:

s = ""

t = {"a", "b", "c", 123, 456, 789} -- sample table
t.someKey = "some value" -- just an extra key value, to show that keys can be strings too

for k, v in pairs(t) do
    s = s .. k .. ":" .. v .. "\n" -- concatenate key/value pairs, with a newline in-between
end

print(s)

Of course, if the value of a key is another table {}, then you will need some extra logic to recursively iterate over these nested tables. I’ll leave that for you as an exercise :)

EDIT 1: Print table as string, showing variable values

s = ""
local ID = 123
local Numbers = 456
local Log = { {Group = ID, Pos = Numbers}, {Group = ID, Pos = Numbers} }

s = s .. "{"
for k, v in next, Log do
    s = s .. "{"

    for vk, vv in next, v do
        if next(v, vk) ~= nil then
            s = s .. vk .. " = " .. vv .. ", "
        else
            s = s .. vk .. " = " .. vv  
        end
    end

    if next(Log, k) ~= nil then
        s = s .. "}, "
    else
        s = s .. "}"
    end

end
s = s .. "}"

print(s)

EDIT 2: Print table as string, showing variable names

s = ""
local ID = 123
local Numbers = 456
local Log = { {Group = ID, Pos = Numbers}, {Group = ID, Pos = Numbers} }

s = s .. "{"
for k, v in next, Log do
    s = s .. "{"

    i = 1
    for vk, vv in next, v do
        name = debug.getlocal(1, i)
        if next(v, vk) ~= nil then
            s = s .. vk .. " = " .. name .. ", "
        else
            s = s .. vk .. " = " .. name
        end
        i = i + 1
    end

    if next(Log, k) ~= nil then
        s = s .. "}, "
    else
        s = s .. "}"
    end

end
s = s .. "}"

print(s)

edited Mar 5, 2020 at 14:28

Gamora

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answered Jun 21, 2018 at 1:23

brianolive

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7 Comments

A Hamburgler Over a year ago

Close but not exactly what I needed. I need to literally take my array and put it into the other file exactly how it is. So an example of my array would be Log = { {Group = ID, Pos = Numbers}, {Group = ID, Pos = Numbers} }

brianolive Over a year ago

@AHamburgler I’ve edited my answer. I am sure there are other permutations to this solution, ways to tweak the logic, etc. Getting variable names (edit 2, above) relies on the table values actually being local upvalues, sooo the final solution depends on your exact situation. I hope this helps you arrive at the code you need.

A Hamburgler Over a year ago

Really appreciate you help it does work except for some reason it wont transfer the variables over. Example it will say group = self instead of 123.

brianolive Over a year ago

@AHamburgler Glad to help. “self” must be defined somewhere in your code. It is not a built-in symbol in Lua (the concept of self is, with the colon operator, but not the name “self”. Up to you if you want to post more code - we could try to get this question across the finish line.

A Hamburgler Over a year ago

I literally took you code and tested it and it came out the other end with group = self and Pos = event. They are not defined anywhere.

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