Erlang的计时器:运行时apply_after/4崩溃

Question

我指的是after-4

2> c(counter).
{ok,counter}
3> counter:start().
** exception error: undefined function timer:apply_after/4
     in function  counter:start/0 (counter.erl, line 40)

-module(counter).
-compile(export_all).

counter(State) ->
  receive
    {From, {add, Number}} ->
      NewNumber = State+Number,
      From ! {self(), NewNumber},
      counter(NewNumber);
    {From, {resolve}} ->
          From ! {self(), State},
          counter(0);
     terminate ->
       ok
   end.

add(Pid, Number) ->
  timer:apply_after(1000, ?MODULE, fun add/2, [Pid, 10]),
  Pid ! {self(), {add, Number}},
  receive
    {Pid, Msg} -> Msg
  after 3000 ->
    timeout
  end.

resolve(Pid) ->
  Pid ! {self(), {resolve}},
  receive
    {Pid, Msg} -> Msg
  after 3000 ->
    timeout
  end.

handle_info(resolve) ->
  resolve(self()),
  erlang:send_after(3000, self(), resolve).

start() ->
  Pid = spawn(?MODULE, counter, [0]),
  timer:apply_after(1000, ?MODULE, fun add/2, [Pid, 10]),
  Pid.

为什么计时器模块没有正确加载？

Answer 1

docs显式地声明函数应该是一个原子。你这是在传递乐趣。将“趣味添加/2”更改为简单的“添加”，并确保add/2已导出。