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elixirphoenix-frameworkecto

How do I generalize this Ecto/Elixir function?

I've got the following, which applies a WHERE statement to an ecto query if platform exists.

  defp maybe_platform(queryable, false), do: queryable
  defp maybe_platform(queryable, platform) do
      queryable
      |> where([c], c.platform == ^platform)
  end

How can I generalise this code for any variable (instead of just platform)? (it's the c.platform bit I'm struggling with)

Solution

  • You need to use Ecto field https://hexdocs.pm/ecto/Ecto.Query.API.html#field/2

    Your function would look something like this

    defp maybe_field(queryable, field_name, field_value) do
    queryable
    |> where([c], field(c, ^field_name) == ^field_value)
end

    and then

    (from m in MyModel)
|> maybe_field(:platform, "platform_name_or_variable")
|> maybe_field(:another_field, "some value")
|> maybe_field(:is_platform_enabled, true)
|> Repo.all