CODEWITHSUNDEEP
for-looplua
Rob Stevens
Rob Stevens

Reputation: 15

Lua - Create a nested table using for loop

I'm a very new to lua so am happy to read material if it will help with tables.

I've decoded a json object and would like to build a table properly using its data, rather than writing 64 lines of the below:

a = {}
  a[decode.var1[1].aId] = {decode.var2[1].bId, decode.var3[1].cId}
  a[decode.var1[2].aId] = {decode.var2[2].bId, decode.var3[2].cId}
  a[decode.var1[3].aId] = {decode.var2[3].bId, decode.var3[3].cId}
  ...etc

Because the numbers are consecutive 1-64, i presume i should be able to build it using a for loop. Unfortunately despite going through table building ideas I cannot seem to find a way to do it, or find anything on creating nested tables using a loop.

Any help or direction would be appreciated.

Upvotes: 0

Views: 804

Answers (2)

Seniru Pasan
Seniru Pasan

Reputation: 801

What you can do is generating a new table with all the contents from the decoded JSON with a for loop.

For example,

function jsonParse(jsonObj)
    local tbl = {}
    for i = 1, 64 do
        a[decodevar.var1[i].aId] = {decode.var2[i].bId, decode.var3[i].cId}
    end
    return tbl
end

To deal with nested cases, you can recursively call that method as follows

function jsonParse(jsonObj)
    local tbl = {}
    for i = 1, 64 do
        a[decodevar.var1[i].aId] = {decode.var2[i].bId, decode.var3[i].cId}
        if type(decode.var2[i].bId) == "table" then
             a[decodevar.var1[i].aid[0] = jsonParse(decode.var2[i].bId)
        end
    end
end

By the way, I can't understand why are you trying to create a table using a table that have done the job you want already. I assume they are just random and you may have to edit the code with the structure of the decodevar variable you have

Upvotes: 0

Personage
Personage

Reputation: 484

Lua for-loops are, at least in my opinion, pretty easy to understand:

for i = 1, 10 do
   print(i)
end

This loop inclusively prints the positive integers 1 through 10.

Lua for-loops also take an optional third argument--which defaults to 1--that indicates the step of the loop:

for i = 1, 10, 2 do
   print(i)
end

This loop prints the numbers 1 through 10 but skips every other number, that is, it has a step of 2; therefore, it will print 1 3 5 7 9.

In the case of your example, if I understand it correctly, it seems that you know the minimum and maximum bounds of your for loops, which are 1 and 64, respectively. You could write a loop to decode the values and put them in a table like so:

local a = {}

for i = 1, 64 do
    a[decodevar.var1[i].aId] = {decode.var2[i].bId, decode.var3[i].cId}
end

Upvotes: 1

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