使用 via 元组注册 GenServer 时遇到问题。 ** (UndefinedFunctionError) function PokerServer.whereis_name/1 未定义或私有)

Question

Here's a very simple GenServer. I am trying to register it on initialization using a via tuple.

defmodule PokerServer do
  use GenServer

  def start(id) do
    GenServer.start(__MODULE__, id, name: {:via, __MODULE__, id})
  end

  @impl GenServer
  def init(id) do
    {:ok, id}
  end
end

Unless I missunderstood something in the documentation , I should be able to pass the via tuple as a name in the third argument of GenServer.start/3

Except that when I try to start the process in the iex shell, I trigger an error

iex(1)> PokerServer.start(123)
** (UndefinedFunctionError) function PokerServer.whereis_name/1 is undefined or private
(live_draft 0.1.0) PokerServer.whereis_name(123)
(stdlib 3.14.2.2) gen.erl:83: :gen.start/6

EDIT: I use elixir 1.12.3 and erlang/OTP 23

Answer 1

The module you pass in {:via, __MODULE__, id} should export register_name/2 , unregister_name/1 , whereis_name/1 and send/2 . For example:

def start(id) do
  GenServer.start(__MODULE__, id, name: {:via, :global, id})
end

One such example is the :global module which uses these functions for keeping the list of names of processes and their associated PIDs that are available globally for a.network of Elixir nodes. Elixir also ships with a local, decentralized and scalable registry called Registry for locally storing names that are generated dynamically. Documentation