How to know if a certain value is within a specific table

Question

I want to identify if a name is inside a list.

lista = {"name","name2","name3"}

*In python I could do if name in lista:, but in moon It’s another way, which I don’t know.

Answer 1

Can make a function to iterate:

function Set (list)
  local set = {}
  for _, l in ipairs(list) do set[l] = true end
  return set
end

And wear it like this

local items = Set { "apple", "orange", "pear", "banana" }

if items["orange"] then
  -- faz algo
end

Or, iterate straight into the list

local items = { "apple", "orange", "pear", "banana" }

for _,v in pairs(items) do
  if v == "orange" then
    -- do something
    break
  end
end

Original: https://stackoverflow.com/a/656232/916193

Alternative, by indexing by names:

local items = { apple=true, orange=true, pear=true, banana=true }
if items.apple then
    ...
end

Original: https://stackoverflow.com/a/656257/916193

Answer 2

If the object in question is an array and contains only primitive values, then the recommended function is:

local function pertence(nome, array)
    for _, valor in ipairs(array) do
        if nome == valor then return true end
    end

    return false
end

-- teste
local a = { 1, 2, 4, 8, 16, 32, 64, 128}
local b = { 'Ana', 'Bia', 'Carla', 'Damares'}

local inner = {1, 2}
local c = { inner, {3, 4}, {5, 6} }

print(pertence(9, a)) -- false
print(pertence(32, a)) -- true
print(pertence('Elena', b)) -- false
print(pertence('Bia', b)) -- true

-- cuidado!
print(pertence({1, 2}, c)) -- false
print(pertence(inner, c)) -- true

Note that the iterator ipairs just sweep the table from 1 to its size. If there are non-integer keys, or numerical keys smaller than 1, or even holes in the table, this method does not work and must be used pairs.

In addition, equality nome == valor can bring undesirable results, if you have tables inside the table, because the comparison is by reference.