Elixir Ecto: Multiple belongs_to relationship in a schema

ecto, elixir, phoenix-framework

Solution

You need to use different names for the relationships:

belongs_to :user_to, FPL.Club, foreign_key: :user_to_id
belongs_to :user_from, FPL.Club, foreign_key: :user_from_id

The name specified here is the field in the struct where Ecto will load the referenced record, which needs to be unique.

Problem

I have the following schema. ``` defmodule Message do use Ecto.Schema schema "messages" do belongs_to :user, FPL.Club, foreign_key: :user_to_id belongs_to :user, FPL.Club, foreign_key: :user_from_id end end ``` As you can see, I have two `belongs_to` relationships I'd like to define here, corresponding to user who sent the message, and the user to whom this message is sent. In the message table, I have two fields named `user_to_id` and `user_from_id`. But this fails with the following error: ``` == Compilation error on file lib/message.ex == ** (ArgumentError) field/association :user is already set on schema lib/ecto/schema.ex:1697: Ecto.Schema.put_struct_field/3 lib/ecto/schema.ex:1677: Ecto.Schema.association/5 lib/ecto/schema.ex:1512: Ecto.Schema.__belongs_to__/4 lib/message.ex:12: (module) (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6 ``` What am I doing wrong?

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