merge two tables in lua

merge-table.lua

function table.merge(t1, t2)
   for k,v in ipairs(t2) do
      table.insert(t1, v)
   end 
 
   return t1
end

TLDR; I understand @dmitrii-eremin that you code helps to clone the contents, but if you can list/highlight the problem in the original answer it will help...

@LRagji Sorry for such a late reply :-)

• The original code goes only though indexed arrays, not through all table elements.
• The original code does not clone objects, it just saves a reference to object to other place. So if the original object is changed, then the cloned is changed as well.

I write a better one! injoin it!

function table_merge(...)
    local tables_to_merge = { ... }
    assert(#tables_to_merge > 1, "There should be at least two tables to merge them")

    for k, t in ipairs(tables_to_merge) do
        assert(type(t) == "table", string.format("Expected a table as function parameter %d", k))
    end

    local result = tables_to_merge[1]

    for i = 2, #tables_to_merge do
        local from = tables_to_merge[i]
        for k, v in pairs(from) do
            if type(k) == "number" then
                table.insert(result, v)
            elseif type(k) == "string" then
                if type(v) == "table" then
                    result[k] = result[k] or {}
                    result[k] = table_merge(result[k], v)
                else
                    result[k] = v
                end
            end
        end
    end

    return result
end

function merge_table(table1, table2)
	for _, value in ipairs(table2) do
		table1[#table1+1] = value
	end
	return table1
end

-- example
local table1 = {1, 2, 3}
local table2 = {4, 5, 6}

merged_table = merge_table(table1, table2)
for _, value in ipairs(merged_table) do
	print(value)
end

output
------------------
1
2
3
4
5
6