Sorting an array of tables

Question

This may be easier than I'm making it on myself. I am relatively new to Lua, but experienced in other languages.

I have a table that looks like this:

local state = {}
state[1] = {
   show = true,
   changed = true,
   progressType = "static",
   value = 0,
   total = 9,
   name = "nine",
}

state[2] = {
   show = true,
   changed = true,
   progressType = "static",
   value = 0,
   total = 7,
   name = "seven",
}

state[3] = {
   show = true,
   changed = true,
   progressType = "static",
   value = 0,
   total = 8,
   name = "eight",
}

state[4] = {
   show = true,
   changed = true,
   progressType = "static",
   value = 0,
   total = 6,
   name = "six",
}

What I need to do is sort each table[] entry based on the value of table.value5. I can't find any functions in the docs that expressely say they do more than just a basic table.sort so I find myself a bit stuck. Do I need to manually sort by iterating through and creating a new table with the sorted data?

Look at table.sort options, and use a 'comp' function to define order. (I'm assuming you want to sort the array part of the list as you can't sort key-value pairs.) — tonypdmtr
– tonypdmtr, Commented Feb 14, 2020 at 14:37
@tonypdmtr I've updated the example table. Given that information, I would want the data moved around such that the data from state[4] would become first because state[4].total is lowest, and the data from state[1] would become last because state[1].total is highest. This is because the parent function reading this data needs it ordered by .total to be displayed. — addohm
– addohm, Commented Feb 14, 2020 at 14:44
table.sort(state,function (a,b) return a.total < b.total end) — tonypdmtr
– tonypdmtr, Commented Feb 14, 2020 at 15:34
@tonypdmtr Why you give answer as comment? There is no possibility to mark question as answered with proper answer. — Leszek Mazur
– Leszek Mazur, Commented Feb 14, 2020 at 18:22

display-name · Accepted Answer · 2020-02-14 20:07:24Z

4

I can't find any functions in the docs that expressely say they do more than just a basic table.sort so I find myself a bit stuck.

I might be misunderstanding your issue, but table.sort is exactly what you need in this case:

local state = {}
state[1] = {
   total = 9,
   name = "nine",
}

state[2] = {
   total = 7,
   name = "seven",
}

state[3] = {
   total = 8,
   name = "eight",
}

state[4] = {
   total = 6,
   name = "six",
}

-- Use table.sort with a custom anonymous function
-- to specify how to compare the nested tables.
table.sort(state, function (a, b) 
    return a.total < b.total
end)

for i=1, #state do
  print(i, state[i].name)
end

With table.sort you can provide an optional custom function, which can be as easy or complicated as you want it to be. In this case (as per your question) it is enough to simply compare the total values of your table.

edited Feb 14, 2020 at 20:07

answered Feb 14, 2020 at 18:53

display-name

4614 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

addohm Over a year ago

I understand. I didn't find anything that expressly showed me that table.sort would iterate through. Thanks.

Collectives™ on Stack Overflow

Sorting an array of tables

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related