In Elixir, is there any way to get a module to list its functions?

Question

In the same way that we can get any object (or class) in Ruby to list its methods, is there any function in Elixir to list all functions belonging to a module? Something (at least remotely) like String.functions (where String could be replaced by any other module name)?

Answer 1

Each module in Elixir defines an __info__ function you can call to get information about that module.

According the Elixir Docs, 1.6.6 e.g., you can pass it :functions to get a list of functions that module contains.

Map.__info__(:functions)

[delete: 2, drop: 2, equal?: 2, fetch: 2, fetch!: 2, from_struct: 1, get: 2,
 get: 3, has_key?: 2, keys: 1, merge: 2, merge: 3, new: 0, pop: 2, pop: 3,
 put: 3, put_new: 3, size: 1, split: 2, take: 2, to_list: 1, update: 4,
 update!: 3, values: 1]

Answer 2

Since Elixir is also Erlang, there is an Erlang way to do this as well.

Every Elixir and Erlang module has the function module_info defined at compile time. There are two arities of this function. For example:

iex(1)> Atom.module_info
 [module: Atom,
 exports: [__info__: 1, to_string: 1, to_char_list: 1, module_info: 0,
 module_info: 1], attributes: [vsn:       [66271031909514292894123295368320335064]],
 compile: [options: [:debug_info], version: '6.0.1',
 time: {2015, 9, 29, 2, 34, 37},
 source: '/private/tmp/elixir20150928-10892-fvin6a/elixir-1.1.1/lib/elixir/lib/atom.ex'],
 native: false,
 md5: <<49, 219, 86, 35, 141, 153, 70, 174, 245, 100, 68, 5, 62, 231, 60, 216>>]

You can specify a specific attribute to return.

 iex(2)> Atom.module_info(:exports)
  [__info__: 1, to_string: 1, to_char_list: 1, module_info: 0, module_info: 1]

Erlang function verison:

iex(3)> :crypto.module_info(:exports)
 [version: 0, stop: 0, supports: 0, info_lib: 0, hash: 2, hash_init: 1,
 hash_update: 2, hash_final: 1, hmac: 3, hmac: 4, hmac_init: 2, hmac_update: 2,
 hmac_final: 1, hmac_final_n: 2, block_encrypt: 4, block_encrypt: 3,
 block_decrypt: 3, next_iv: 2, next_iv: 3, stream_init: 3, stream_init: 2,
 stream_encrypt: 2, stream_decrypt: 2, rand_bytes: 1, strong_rand_bytes: 1,
 rand_bytes: 3, rand_uniform: 2, rand_seed: 1, mod_pow: 3, verify: 5, sign: 4,
 public_encrypt: 4, private_decrypt: 4, private_encrypt: 4, public_decrypt: 4,
 exor: 2, generate_key: 2, generate_key: 3, compute_key: 4, md5: 1, md5_init: 0,
 md5_update: 2, md5_final: 1, md4: 1, md4_init: 0, md4_update: 2, md4_final: 1,
 sha: 1, sha_init: 0, sha_update: 2, ...]

This is what the IEx autocomplete function uses that allows you to expand both Elixir and Erlang functions.

Answer 3

I've been using iex(1)> exports TargetModuleName. It lists all functions and macros belonging to a module. I stumbled onto it trying to figure out how to stop Map.__info__(:functions) from truncating a long function list.

Answer 4

Not a function but a way to get module to list its functions in iex is to write the name of the module followed by . then hiting tab:

iex(1)> IO.     ## Hit tab
ANSI                    Stream                  StreamError
binread/1               binread/2               binstream/2
binwrite/1              binwrite/2              chardata_to_string/1
getn/1                  getn/2                  getn/3
gets/1                  gets/2                  inspect/1
inspect/2               inspect/3               iodata_length/1
iodata_to_binary/1      puts/1                  puts/2
read/1                  read/2                  stream/2
warn/1                  warn/2                  write/1
write/2