lua-table-flatten

flatten a table into a table of specified depth.

Installation

luarocks install table-flatten

---

res = flatten( tbl [, maxdepth [, encoder [, setter [, key2str]]]] )

returns a flattened table.

Parameters

• tbl:table: target table.
• maxdepth:integer: maximum depth to flatten. nil or 0 or less are unlimited. (default: 0)
• encoder:function: function that encode the key and value to the string.
• setter:function: function that sets the key and value pair to result table.
• key2str:function: function that generates key from table-name/field-key pair.

Returns

• res:table: a flattened table.

encoder function

the declaration of the encoder function is as follows;

key, val = encoder( key, val )

Parameters

• key:string: a key string in dot notation.
• val:any: a value of key.

Returns

• key:any: used as a key of flattened table.
• val:any: used as a value of key.

setter function

the declaration of the setter function is as follows;

setter( res, key, val )

Parameters

• res:table: a result table.
• key:string: a key string.
• val:any: a value of key.

key2str function

the declaration of the key2str function is as follows;

key = key2str( tname, key )

Parameters

• tname:string: a table name, or nil if a root table.
• key:any: a key.

Returns

• key:string?: used as a key of current field. if nil, ignore the field-value.

Usage

local flatten = require('table.flatten')
-- you must install dump module from https://github.com/mah0x211/lua-dump 
-- or luarocks install dump
local dump = require('dump') 

local tbl = {
    foo = {
        bar = {
            baz = {
                str = 'str-value',
                coro = coroutine.create(function()end)
            },
            num = 123,
        },
        truthy = true,
        empty = {}
    },
    falsy = false,
    func = function() end
}
tbl.circular = {
    description = 'this table contains this table itself, but circular references are ignored.',
    ref = tbl,
}

for depth = 0, 4 do
    print( 'depth#' .. depth .. ' ' .. dump( flatten( tbl, depth ) ) )
end

-- depth#0 {
--     ["circular.description"] = "this table contains this table itself, but circular references are ignored.",
--     ["foo.bar.baz.coro"] = "thread: 0x0004f758",
--     ["foo.bar.baz.str"] = "str-value",
--     ["foo.bar.num"] = 123,
--     ["foo.empty"] = {},
--     ["foo.truthy"] = true,
--     falsy = false,
--     func = "function: 0x0004f7c8"
-- }
-- depth#1 {
--     circular = {
--         description = "this table contains this table itself, but circular references are ignored.",
--         ref = {
--             circular = "<Circular table: 0x0004f7e8>",
--             falsy = false,
--             foo = {
--                 bar = {
--                     baz = {
--                         coro = "thread: 0x0004f758",
--                         str = "str-value"
--                     },
--                     num = 123
--                 },
--                 empty = {},
--                 truthy = true
--             },
--             func = "function: 0x0004f7c8"
--         }
--     },
--     falsy = false,
--     foo = {
--         bar = {
--             baz = {
--                 coro = "thread: 0x0004f758",
--                 str = "str-value"
--             },
--             num = 123
--         },
--         empty = {},
--         truthy = true
--     },
--     func = "function: 0x0004f7c8"
-- }
-- depth#2 {
--     ["circular.description"] = "this table contains this table itself, but circular references are ignored.",
--     ["foo.bar"] = {
--         baz = {
--             coro = "thread: 0x0004f758",
--             str = "str-value"
--         },
--         num = 123
--     },
--     ["foo.empty"] = {},
--     ["foo.truthy"] = true,
--     falsy = false,
--     func = "function: 0x0004f7c8"
-- }
-- depth#3 {
--     ["circular.description"] = "this table contains this table itself, but circular references are ignored.",
--     ["foo.bar.baz"] = {
--         coro = "thread: 0x0004f758",
--         str = "str-value"
--     },
--     ["foo.bar.num"] = 123,
--     ["foo.empty"] = {},
--     ["foo.truthy"] = true,
--     falsy = false,
--     func = "function: 0x0004f7c8"
-- }
-- depth#4 {
--     ["circular.description"] = "this table contains this table itself, but circular references are ignored.",
--     ["foo.bar.baz.coro"] = "thread: 0x0004f758",
--     ["foo.bar.baz.str"] = "str-value",
--     ["foo.bar.num"] = 123,
--     ["foo.empty"] = {},
--     ["foo.truthy"] = true,
--     falsy = false,
--     func = "function: 0x0004f7c8"
-- }