使用HTTPoison初始化模块属性

Question

我正在尝试像这样初始化一个模块属性

  response = HTTPoison.get! url
  {:ok, response} = Poison.decode(response.body)
  @attr response

我以前用过一个文件，像这样的：

  @external_resource file = Path.join([__DIR__, "file.txt"])
  Module.register_attribute __MODULE__, :attr, accumulate: true

  for line <- File.stream!(file, [], :line) do
    @attr line
    ...

不可能对HTTPoison和获取API的响应做同样的操作吗？我收到这个错误：

== Compilation error in file lib/module.ex ==
** (ArgumentError) argument error
    (stdlib) :ets.lookup_element(:hackney_config, :mod_metrics, 2)
    /project/deps/hackney/src/hackney_metrics.erl:27: :hackney_metrics.get_engine/0
    /project/deps/hackney/src/hackney_connect.erl:69: :hackney_connect.create_connection/5
    /project/deps/hackney/src/hackney_connect.erl:37: :hackney_connect.connect/5
    /project/deps/hackney/src/hackney.erl:316: :hackney.request/5
    lib/httpoison/base.ex:630: HTTPoison.Base.request/9
    lib/httpoison.ex:66: HTTPoison.request!/5
    lib/module.ex:4: (module)

Answer 1

依赖的应用程序不会在编译时自动启动。在使用HTTPoison之前，需要显式地启动它：

HTTPoison.start()
response = HTTPoison.get! url
{:ok, response} = Poison.decode(response.body)
@attr response