如何在Elixir Struct中实现to_query(data) [英] How to implement to_query(data) in Elixir Struct

问题描述

我正在尝试使用Repo.update更新数据库中的现有记录:

I am attempting to update a existing records in my database using Repo.update:

  def subscribe_email(conn, %{"email-address"=>email_address, "shop"=>shop}) do
    current_record = Repo.all(%Oauth.EmailAddress{email_address: email_address, active: false, shop: shop, verified: :true})
    current_record = Ecto.Changeset.change(current_record, active: :true)
    case Repo.update current_record do
      {:ok, struct} -> IO.puts "updated correctly."
      {:error, changeset} -> IO.puts "did not update"
    end
  end

我有一个用于％Oauth.EmailAddress的模型:

I have a model for %Oauth.EmailAddress:

defmodule Oauth.EmailAddress do
  use Ecto.Model

  schema "email_address" do
    field :email_address, :string
    field :active, :boolean
    field :shop, :string
    field :verified, :boolean
    timestamps
  end
end

当我点击subscribe_email()时，会引发异常:

When I hit subscribe_email(), an exception is raised:

** (Protocol.UndefinedError) protocol Ecto.Queryable not implemented   for %Oauth.EmailAddress

我知道我需要从Ecto.Queryable实现to_query().但是，我不知道如何做到这一点.尽管我已经阅读了官方文档，但是我还没有使用协议，所以我对Elixir中的协议不熟悉.请说明如何为我的结构实现to_query().

I know that I need to implement to_query() from Ecto.Queryable. However, I do not know how to do this. I am not familiar with Protocols in Elixir, although I have read the official documentation, I have not used Protocols. Please explain how to implement to_query() for my struct.

推荐答案

该错误有点令人误解. Repo.all不接受这样填充字段的结构.您最有可能在寻找这个东西:

That error is a bit misleading. Repo.all doesn't accept a struct with fields filled in like that. You're most likely looking for this:

current_record =
  from(Oauth.EmailAddress)
  |> where(email_address: email_address, active: false, shop: shop, verified: :true)
  |> Repo.all

此外，由于您要将结果传递给Ecto.Changeset.change，因此您可能只需要一个记录，而不是所有记录的列表:

Also, since you're passing the result to Ecto.Changeset.change, you probably want just one record, not a list of all records:

current_record =
  from(Oauth.EmailAddress)
  |> where(email_address: email_address, active: false, shop: shop, verified: :true)
  |> Repo.one

请注意，如果查询有多个匹配记录，则此操作将失败.

Note that this will fail if there's more than one matching record for the query.

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