TopolearnEverything nontrivial in Lua is built from tables, so you need them from day one.
A table is an associative array: any value except nil (and NaN) can be a key. Lua uses tables for arrays, records, sets, objects, modules and namespaces.
Construct one with braces. Positional values get integer keys starting at 1, not 0: {"a", "b"} has t[1] == "a". Named fields {x = 1} are sugar for string keys, and t.x is sugar for t["x"]. Use brackets for any other key: {[10] = "ten", ["my key"] = true}.
Reading a missing key returns nil. Assigning nil deletes the key.
The length operator #t gives the length of the sequence part: it is only well defined when the integer keys are 1..n with no nil holes. For arrays use t[#t + 1] = v or table.insert(t, v) to append, table.remove(t) to pop, table.concat to join strings and table.sort to sort in place.
Tables are reference values: assigning a table to another variable doesn't copy it, and two tables are == only if they are the same table. That makes them cheap to pass around, but you need to copy explicitly when you want an independent value.
Example
local fruits = {"apple", "banana"}
fruits[#fruits + 1] = "cherry"
table.insert(fruits, 1, "kiwi") -- insert at position 1
print(#fruits, fruits[1]) --> 4 kiwi
print(table.concat(fruits, ", ")) --> kiwi, apple, banana, cherry
local point = {x = 3, y = 4, ["z-axis"] = 0}
point.x = nil -- delete a key
print(point.x, point["z-axis"]) --> nil 0
local alias = fruits
alias[1] = "lime"
print(fruits[1]) --> lime (same table)
print({} == {}) --> false
table.sort(fruits)
print(table.concat(fruits, " ")) --> apple banana cherry lime
print(table.remove(fruits), #fruits) --> lime 3Remember
- Tables are the only data structure: arrays, maps, objects, modules
- Arrays start at index 1;
t.xmeanst["x"] #tis reliable only for sequences without nil holes- Tables are references, compared by identity
Watch out for
- Storing nil in the middle of an array, which makes
#tand ipairs unreliable.