Lua - print table keys in order of insertion

Question

house = {
         ["Street 22"] = {
                           {name = "George", age = 20},
                           {name = "Pete", age = 25}
                         },
         ["Street 30"] = {
                           {name = "John", age = 32},
                         }
       }

I want to print the keys/streets of the houses tables in the exact order they are. If I use:

for i, v in pairs(house) do
    print(i)
end

that's going to print them, but the order seems a bit random... How can I print them in order they are inserted?

Answer 1

As lhf answer already stated, you won't be able to do this with just the associative map part of the table. But you can do it if you maintain the insertion order using the array-index part of the table. eg.

table.insert(house, "Street 22")
local street = house[#house]
house[street] = { {name = "George", age = 20},
                  {name = "Pete", age = 25} }

table.insert(house, "Street 30")
street = house[#house]
house[street] = { {name = "John", age = 32} }

Afterwards you can print it out using ipairs

for _, v in ipairs(house) do
  print(v)
end

Answer 2

Lua tables are sets of key-value pairs. There is no order.

The manual says:

The order in which the indices are enumerated is not specified, even for numeric indices.