Compile error: module Any is reserved and cannot be defined

Say I have the following resources: City:

# myapp/lib/myapp/data/resources/city.ex
defmodule MyApp.Data.City do
  use Ash.Resource
    
  actions do
    defaults [:create, :update, :read, :destroy]
  end

  attributes do
    uuid_primary_key :id
    attribute :name, :string do
      allow_nil? false
    end
  end

  relationships do
    has_one :state, MyApp.Data.State
  end
end

# myapp/lib/myapp/data/resources/city.ex
defmodule MyApp.Data.City do
  use Ash.Resource
    
  actions do
    defaults [:create, :update, :read, :destroy]
  end

  attributes do
    uuid_primary_key :id
    attribute :name, :string do
      allow_nil? false
    end
  end

  relationships do
    has_one :state, MyApp.Data.State
  end
end

State:

defmodule MyApp.Data.State do
  @moduledoc false
  use Ash.Resource

  actions do
    defaults [:create, :update, :read, :destroy]
  end

  attributes do
    uuid_primary_key :state_id
    attribute :name, :string do
      allow_nil? false
    end
    attribute :url, :string do
      allow_nil? true
    end
  end

  relationships do
    has_one :region, MyApp.Data.Region
  end
end

defmodule MyApp.Data.State do
  @moduledoc false
  use Ash.Resource

  actions do
    defaults [:create, :update, :read, :destroy]
  end

  attributes do
    uuid_primary_key :state_id
    attribute :name, :string do
      allow_nil? false
    end
    attribute :url, :string do
      allow_nil? true
    end
  end

  relationships do
    has_one :region, MyApp.Data.Region
  end
end

Region:

defmodule MyApp.Data.Region do
  @moduledoc false
  use Ash.Resource

  actions do
    defaults [:create, :update, :read, :destroy]
  end

  attributes do
    uuid_primary_key :region_id
    attribute :name, :string do
      allow_nil? false
    end
  end
end

defmodule MyApp.Data.Region do
  @moduledoc false
  use Ash.Resource

  actions do
    defaults [:create, :update, :read, :destroy]
  end

  attributes do
    uuid_primary_key :region_id
    attribute :name, :string do
      allow_nil? false
    end
  end
end

Credo seems to complain about state, saying:

** (CompileError) iex:1: module Any is reserved and cannot be defined
Elixir reserves the following module names: Elixir, Any, BitString, PID, and Reference.

(ArgumentError) schema does not have the field :id used by association :region, please set the :references option accordingly

Stacktrace:
  │ (ecto 3.9.4) lib/ecto/association.ex:696: Ecto.Association.Has.struct/3
  │ (ecto 3.9.4) lib/ecto/schema.ex:1879: Ecto.Schema.association/5
  │ (ecto 3.9.4) lib/ecto/schema.ex:2006: Ecto.Schema.__has_one__/4
  │ /Users/alec-s/Projects/myapp/lib/myapp/data/resources/state.ex:1: (file)
  │ /Users/alec-s/Projects/myapp/lib/myapp/data/resources/state.ex:1: (file)
  │ (stdlib 4.2) erl_eval.erl:748: :erl_eval.do_apply/7
  │ (stdlib 4.2) erl_eval.erl:136: :erl_eval.exprs/6Elixir

** (CompileError) iex:1: module Any is reserved and cannot be defined
Elixir reserves the following module names: Elixir, Any, BitString, PID, and Reference.

(ArgumentError) schema does not have the field :id used by association :region, please set the :references option accordingly

Stacktrace:
  │ (ecto 3.9.4) lib/ecto/association.ex:696: Ecto.Association.Has.struct/3
  │ (ecto 3.9.4) lib/ecto/schema.ex:1879: Ecto.Schema.association/5
  │ (ecto 3.9.4) lib/ecto/schema.ex:2006: Ecto.Schema.__has_one__/4
  │ /Users/alec-s/Projects/myapp/lib/myapp/data/resources/state.ex:1: (file)
  │ /Users/alec-s/Projects/myapp/lib/myapp/data/resources/state.ex:1: (file)
  │ (stdlib 4.2) erl_eval.erl:748: :erl_eval.do_apply/7
  │ (stdlib 4.2) erl_eval.erl:136: :erl_eval.exprs/6Elixir

Not really sure what to do about that.

13 Replies

jart•3y ago

Hey there. So it's because the relationships expect the related schemas to have an ID field called :id - so for example in your has_one :state State in City you need to add destination_attribute. See the DSL docs for more information: https://ash-hq.org/docs/dsl/ash-resource#relationships-has_one-destination_attribute

dblack•3y ago

I'd use belongs_to instead of has_one in this example (has_one puts the foreign key on the other table)

jart•3y ago

right but you need to set source_attribute and destination_attribute appropriately so that ash knows which fields contain the foreign keys

dblack•3y ago

Yep, absolutely

AlecStewart1#1125OP•3y ago

Hmm I'm pretty sure I did that earlier and it still complained. Let me add it in again. This works:

    belongs_to :region, MyApp.Data.Region do
      source_attribute :region_id
      destination_attribute :region
    end

    belongs_to :region, MyApp.Data.Region do
      source_attribute :region_id
      destination_attribute :region
    end

So for when you want foreign keys, belongs_to is what's preferable?

dblack•3y ago

Yeah, I think of has_one as being like has_many (you'd use on the other side of the relationship)

AlecStewart1#1125OP•3y ago

Oh so has_one would be in the region resource, not the state resource?

dblack•3y ago

also, you could use uuid_primary_key :id on all those resources, and not need to provide the source and destination attributes to belongs_to Yep, you could but i think you'll want has_many ie, a region has many states i might be misunderstanding the relationship though

AlecStewart1#1125OP•3y ago

Okay, makes sense. I'm more or less trying to replicate something for work, because in the future we're considering moving away from our Java codebase and I'd like to have something to propose. So maybe has_many might work, considering a state has a region attribute that has the Java annotation @ManyToOne.

dblack•3y ago

yep, so you'd have has_many on one side, and belongs_to on the other. If you've got a @OneToOne, you'll want a belongs_to on one side (the side with the foreign key) and a has_one on the other

AlecStewart1#1125OP•3y ago

Ah, now it makes more sense.

dblack•3y ago

I think of belongs_to as defining the relationship (it sets the foreign key on that resource) and has_one and has_many as utilities to go 'the other way' (if required) if that makes sense

AlecStewart1#1125OP•3y ago

Makes sense.

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Compile error: module Any is reserved and cannot be defined

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