从下面的代码中,当我拨打conn.params["geo"]
时,我收到以下错误:
test/plugs/geoip_test.exs:4
** (UndefinedFunctionError) function Plug.Conn.Unfetched.fetch/2 is undefined (Plug.Conn.Unfetched does not implement the Access behaviour)
stacktrace:
(plug) Plug.Conn.Unfetched.fetch(%{:__struct__ => Plug.Conn.Unfetched, :aspect => :params, "geo" => "Mountain View, US", "ip" => "8.8.8.8"}, "geo")
...
defmodule AgilePulse.Plugs.GeoIPTest do
use AgilePulse.ConnCase
test "returns Mountain View for 8.8.8.8" do
conn = build_conn
params = Map.put(conn.params, "ip", "8.8.8.8")
conn = Map.put(conn, :params, params) |> AgilePulse.Plugs.GeoIP.call(%{})
assert conn.params["geo"] == "Mountain View, US"
end
end
defmodule AgilePulse.Plugs.GeoIP do
import Plug.Conn
def init(opts), do: opts
def call(%Plug.Conn{params: %{"ip" => ip}} = conn, _opts) do
geo = set_geo(ip)
params = Map.put(conn.params, "geo", geo)
Map.put(conn, :params, params)
end
def call(conn, _opts), do: conn
...
end
有人可以告诉我为什么会失败以及适当的解决方案是什么? TY!
答案 0 :(得分:5)
简短回答:改变一下:
params = Map.put(conn.params, "ip", "8.8.8.8")
要:
params = %{"ip": "8.8.8.8"}
说明:Phoenix.ConnTest.build_conn/0
返回Conn
,params
设置为%Plug.Conn.Unfetched{}
。通过使用Map.put
,您不会重置__struct__
的值,而只会添加新密钥:
%Plug.Conn{ ...,
params: %{:__struct__ => Plug.Conn.Unfetched, :aspect => :params,
"ip" => "8.8.8.8"}, ... }
当您稍后致电params["geo"]
时,Elixir会看到params
是一个结构,并尝试在结构模块上调用fetch/2
函数,而该模块并非如此。存在。要将params
重置为普通地图(以便Elixir在使用方括号语法时调用Map.get
),您只需执行params = %{"ip": "8.8.8.8"}
。