（FunctionClauseError）Access.get / 3中没有匹配的功能子句 [英] (FunctionClauseError) no function clause matching in Access.get/3

问题描述

我不熟悉Elixir，目前正在与Ruby进行交易。我正在努力解决我遇到的错误，并且由于Elixir没有 object.class ，我正在努力了解返回的数据类型以及如何进行故障排除它。

I am new to Elixir and currently making a transaction from Ruby. I am struggling to get around an error I am getting and because Elixir does not have object.class, I am struggling to understand what data type am I returning back and how to troubleshoot it.

无论如何，我试图从CSV播种数据库但出现错误

Anyway I am trying to seed a database from a CSV but getting the error

下面是我的代码

File.stream!('users_departs.csv')
|> Stream.drop(1)
|> CSV.decode(headers: [:name, :title, :departments])
|> Enum.take(10
|> Enum.each( fn(x) -> IO.inspect(x[:ok]) end )

 Error

** (FunctionClauseError) no function clause matching in Access.get/3

The following arguments were given to Access.get/3:

    # 1
    {:ok,
     %{
       departments: "Sales|Marketing",
       name: "John Smith",
       title: "Customer Service"
     }}

    # 2
    :ok

    # 3
    nil
(elixir) lib/access.ex:306: Access.get/3
(stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
(stdlib) erl_eval.erl:878: :erl_eval.expr_list/6

我有2个模型：用户和部门，我想先给部门播种，然后创建一个用户，然后关联一个用户部门映射，但是

I have 2 models, User, and Departments and I would like to seed the departments first, then create a user and then associate a user-department mapping but am struggling to get past this step.

任何帮助将不胜感激

推荐答案

Access.get / 3 是一种长生不老药功能，根据文档所述：

Access.get/3 is a elixir function, that, according to the documentation:

获取容器中给定键的值（实现 Access 行为的映射，关键字列表或结构）

Gets the value for the given key in a container (a map, keyword list, or struct that implements the Access behaviour)

检查错误消息，

{:ok,
   %{
     departments: "Sales|Marketing",
     name: "John Smith",
     title: "Customer Service"}}

不是地图，关键字列表或结构等。它是一个 tuple ，由：ok 原子和地图。

is not "map, keyword list or struct etc." It is a tuple, consisting of :ok atom and the map.

似乎是 CSV.decode（标题： [：name，：title，：departments]）返回 {：ok，value_decode} 。

因此您无法将其通过管道传输到 Enum.take / 2 。

So you can not pipe it to Enum.take/2 as is.

只是

{:ok, decode_csv} =
  File.stream!('users_departs.csv')
  |> Stream.drop(1)
  |> CSV.decode(headers: [:name, :title, :departments])

decode_csv
|> Enum.take(10)
|> Enum.each( fn(x) -> IO.inspect(x[:ok]) end )

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