如何在Ecto查询中插入字段? [英] How do interpolation fields in Ecto queries?

问题描述

Ecto文档显示了如何进行插值.但是我在查询中需要动态字段.我有数十个字段，并且为每个字段编写查询似乎并不连贯.

The Ecto documentation shows how to do interpolation values. But I need dynamic fields in my queries. I have dozens of fields and write queries for each of them does not seem cohesive.

defmodule Hedone.SearchController do
  use Hedone.Web, :controller

  alias Hedone.User

  def idade(conn, %{"idade+" => maior, "idade-" => menor, "campo" => campo}) do
    IO.inspect campo
  query = from u in User, where: u.campo > ^maior and u.campo < ^menor, select: u.name
  pesquisa = Repo.all query
  IO.inspect pesquisa
  text conn, "Works"
end

end

此控制器生成以下错误:

This controller generates the following error:

** (Ecto.QueryError) web/controllers/search.ex:8: field `Hedone.User.campo` in `where` does not exist in the schema in query:

from u in Hedone.User,
  where: u.campo > ^18 and u.campo < ^40,
  select: u.name

自动翻译.

推荐答案

我假设 campo 包含一个字符串，其中包含您要使用的字段的名称，例如年龄" .您可以在其中使用 field 查询此:

I'm assuming campo contains a string with the name of the field you want to use, e.g. "age". You can use field in the query for this:

def idade(conn, %{"idade+" => maior, "idade-" => menor, "campo" => campo}) do
  campo = String.to_existing_atom(campo)
  query = from u in User, where: field(u, ^campo) > ^maior and field(u, ^campo) < ^menor, select: u.name
  pesquisa = Repo.all query
  IO.inspect pesquisa
  text conn, "Works"
end

field 期望该字段是一个原子，因此我使用了 String.to_existing_atom 安全地将字符串转换为atom.由于您必须已经在模型的架构中定义了字段，因此 String.to_existing_atom 不会因任何有效的字段名称而失败.

field expects the field to be an atom, so I've used String.to_existing_atom to safely convert a string to atom. Since you already must have defined the field in the schema of the model, String.to_existing_atom will not fail for any valid field name.

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