如何在phoenix elixir框架中访问map内部的值

我有

message=%{“to”=>“testuser”，“value”=>“asdads”}

map。我需要访问此地图中“to”键的值

message.to
message[:to]
Map.fetch!(message, to)

到目前为止什么都没用

这是控制台错误消息

[error] GenServer #PID<0.395.0> terminating
** (KeyError) key :to not found in: %{"to" => "testuser", "value" => "aadadadad"}
    (phoenix_chat) web/channels/room_channel.ex:31: PhoenixChat.RoomChannel.handle_in/3
    (phoenix) lib/phoenix/channel/server.ex:225: anonymous fn/4 in Phoenix.Channel.Server.handle_info/2
    (stdlib) gen_server.erl:601: :gen_server.try_dispatch/4
    (stdlib) gen_server.erl:667: :gen_server.handle_msg/5
    (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3
Last message: %Phoenix.Socket.Message{event: "message:new", payload: %{"to" => "testuser", "value" => "aadadadad"}, ref: "4", topic: "room:Pamidu"}
State: %Phoenix.Socket{assigns: %{user: "Pamidu"}, channel: PhoenixChat.RoomChannel, channel_pid: #PID<0.395.0>, endpoint: PhoenixChat.Endpoint, handler: PhoenixChat.UserSocket, id: nil, joined: true, pubsub_server: PhoenixChat.PubSub, ref: nil, serializer: Phoenix.Transports.WebSocketSerializer, topic: "room:Pamidu", transport: Phoenix.Transports.WebSocket, transport_name: :websocket, transport_pid: #PID<0.384.0>}

[error]GenServer#PID终止
**（KeyError）键：在以下位置找不到：%%{“to”=>“testuser”，“value”=>“aadadad”}
（phoenix_chat）web/channels/room_channel.ex:31:PhoenixChat.RoomChannel.handle_in/3
（phoenix）lib/phoenix/channel/server.ex:225:phoenix.channel.server.handle_info/2中的匿名fn/4
（stdlib）gen_server.erl:601:：gen_server.try_dispatch/4
（stdlib）gen_server.erl:667:：gen_server.handle_msg/5
（stdlib）proc_lib.erl:247:：proc_lib.init_p_do_apply/3
最后一条消息：%Phoenix.Socket.message{event:“message:new”，负载：%{“to”=>“testuser”，“value”=>“aadadad”}，参考：“4”，主题：“room:Pamidu”}
状态：%Phoenix.Socket{assignments:%%{user:“Pamidu”}，通道：PhoenixChat.RoomChannel，通道：PhoenixChat.pid:#pid，端点：PhoenixChat.endpoint，处理程序：PhoenixChat.UserSocket，id:nil，joined:true，pubsub\u服务器：PhoenixChat.pubsub，ref:nil，序列化程序：PhoenixChat.Transports.WebSocketSerializer，主题：“房间：Pamidu”，传输：Phoenix.Transports.WebSocket，传输名称：：WebSocket，传输pid:#pid}

地图的关键点是字符串，而不是原子。您发布的所有三个代码段都将访问键

：to

（atom），而不是

“to”

（string）

---

您可以执行

message[“to”]

来访问该值。您还可以执行

Map.fetch！（消息“to”）

如果您想在值不存在时引发错误。

您可以执行以下操作

case Map.fetch(message,"to") do
   {:ok, value} -> IO.inspect value;           #Success  
   :error       -> IO.inspect "Key Not found"  #Error
end

---

message[“to”]

？声明中还包括

按摩

非

消息