用lua排序嵌套表

Question

I have following table:

{
  STANDBY = {
    timeout = "10",
    mode = "0"
  },
  RTP = {
    minport = "10000",
    maxport = "10010"
  }
}

I want to sort it alphabetically, so the resulting table should be something like this:

{
  RTP = {
    maxport = "10010",
    minport = "10000"
  },
  STANDBY = {
    mode = "0",
    timeout = "10"
  },
}

Can you please help me?

Answer 1

Quoting the following from Programming in Lua : 19.3 .

A common mistake is to try to order the indices of a table. In a table, the indices form a set, and have no order whatsoever. If you want to order them, you have to copy them to an array and then sort the array.

If you traverse a table with pairs() , the names appear in an arbitrary order. However, you cannot sort them directly, because these names are keys of the table.

The workaround is also mentioned on the same page.

local tableVarName = {
    STANDBY = {
        timeout = "10",
        mode = "0"
    },
    RTP = {
        minport = "10000",
        maxport = "10010"
    }
}
function pairsByKeys (t, f)
  local a = {}
  for n in pairs(t) do table.insert(a, n) end
  table.sort(a, f)
  local i = 0      -- iterator variable
  local iter = function ()   -- iterator function
    i = i + 1
    if a[i] == nil then return nil
    else return a[i], t[a[i]]
    end
  end
  return iter
end
for name, line in pairsByKeys(tableVarName) do
  print(name, line)
end