錯誤 - 在靈藥

Question

我運行下面的代碼實現協議：

ExHubic.Request.request({:get, "/account", nil, :hubic}, ExHubic) 

，並得到以下錯誤：

** (Protocol.UndefinedError) protocol ExHubic.Request not implemented for {:get, "/account", nil, :hubic} 
    (ex_hubic) lib/request.ex:1: ExHubic.Request.impl_for!/1 
    (ex_hubic) lib/request.ex:6: ExHubic.Request.request/2 

此錯誤消息建議，我認爲該協議未實現對於定義爲@type t :: {atom, String.t, any, :hubic}的ExHubic.Query.Hubic.t類型

這可能是我創建的類型的問題，但我看不到它。

一些背景：

defprotocol ExHubic.Request do 
    @moduledoc false 
    @spec request(query :: ExHubic.Query.t, client :: atom) 
       :: ExHubic.Query.http_query_t 
    def request(query, client) 
end 

defimpl ExHubic.Request, for: ExHubic.Query.Hubic do 
    @spec request(query :: ExHubic.Query.Hubic.t, client :: atom) 
       :: {:ok, ExHubic.Client.response_t} | {:error, ExHubic.Client.response_t} 
    def request({method, uri, params, :hubic} = query, client) do 
    implementation_details 
    end 
end 

defmodule ExHubic.Query do 
    @moduledoc false 
    @type t :: {atom, String.t, any, atom} 
end 

defmodule ExHubic.Query.Hubic do 
    @type t :: {atom, String.t, any, :hubic} 
    @spec account() :: __MODULE__.t 
    def account(), do: {:get, "/account", :nil, :hubic} 
end 

Answer 1

有幾個問題在這裏，首先，你正在使用的協議的原子（模塊名稱）。您需要使用內置類型或結構，如http://elixir-lang.org/getting-started/protocols.html#protocols-and-structs中所述。這意味着將defstruct到模塊：

defmodule ExHubic.Query.Hubic do 
    defstruct [:method, :uri, :params, service: :hubic] 
    @type t :: %__MODULE__{method: atom, uri: String.t, params: any, service: :hubic} 
    def account(), do: {:get, "/account", :nil, :hubic} 
end 

defprotocol ExHubic.Request do 
    def request(query, client) 
end 


defimpl ExHubic.Request, for: ExHubic.Query.Hubic do 

    @spec request(Query.t, atom) :: any 
    def request(query, client) do 
    IO.inspect query 
    end 
end 

然後，您可以利用此功能：

ExHubic.Request.request(%ExHubic.Query.Hubic{method: :get, params: nil, service: :hubic, uri: "/account"}, client)