AE
Ash Elixir•2y ago
morfertaw

Understanding "manage_relationship"

So I have a many_to_many relationship between the following resources. Reactant 
defmodule Flame.App.Resources.Reactant do
...
  attributes do
    ...
    attribute :identity, :string do
      allow_nil? false
      constraints trim?: false, max_length: 20, min_length: 4, allow_empty?: false
    end
    ...
  end

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

    create :define do
      upsert? true

      argument :source_definitions, {:array, :map}

      change manage_relationship(:source_definitions, :sources,
               on_lookup: :relate,
               on_no_match: :create,
               on_match: :update,
               on_missing: :unrelate
             )
    end

    update :redefine do
      argument :source_definitions, {:array, :map}

      change manage_relationship(:source_definitions, :sources,
               on_lookup: :relate,
               on_match: :update,
               on_no_match: :create,
               on_missing: :unrelate
             )
    end
  end

  relationships do
    many_to_many :sources, Flame.App.Resources.Source do
      through Flame.App.Resources.ReactantSource
      source_attribute_on_join_resource :reactant_id
      destination_attribute_on_join_resource :source_id
    end
  end
...
end
defmodule Flame.App.Resources.Reactant do
...
  attributes do
    ...
    attribute :identity, :string do
      allow_nil? false
      constraints trim?: false, max_length: 20, min_length: 4, allow_empty?: false
    end
    ...
  end

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

    create :define do
      upsert? true

      argument :source_definitions, {:array, :map}

      change manage_relationship(:source_definitions, :sources,
               on_lookup: :relate,
               on_no_match: :create,
               on_match: :update,
               on_missing: :unrelate
             )
    end

    update :redefine do
      argument :source_definitions, {:array, :map}

      change manage_relationship(:source_definitions, :sources,
               on_lookup: :relate,
               on_match: :update,
               on_no_match: :create,
               on_missing: :unrelate
             )
    end
  end

  relationships do
    many_to_many :sources, Flame.App.Resources.Source do
      through Flame.App.Resources.ReactantSource
      source_attribute_on_join_resource :reactant_id
      destination_attribute_on_join_resource :source_id
    end
  end
...
end
Source 
defmodule Flame.App.Resources.Source do
...
  attributes do
    uuid_primary_key :id

    attribute :description, :string do
      allow_nil? false
    end

    create_timestamp :created_at
    update_timestamp :updated_at
  end

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

  identities do
    identity :unique_description, [:description]
  end
...
end
defmodule Flame.App.Resources.Source do
...
  attributes do
    uuid_primary_key :id

    attribute :description, :string do
      allow_nil? false
    end

    create_timestamp :created_at
    update_timestamp :updated_at
  end

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

  identities do
    identity :unique_description, [:description]
  end
...
end
3 Replies
morfertaw
morfertawOP•2y ago
ReactantSource 
defmodule Flame.App.Resources.ReactantSource do
  ...
  actions do
    defaults [:create, :read, :update, :destroy]
  end

  relationships do
    belongs_to :reactant, Flame.App.Resources.Reactant, primary_key?: true, allow_nil?: false
    belongs_to :source, Flame.App.Resources.Source, primary_key?: true, allow_nil?: false
  end
...
end
defmodule Flame.App.Resources.ReactantSource do
  ...
  actions do
    defaults [:create, :read, :update, :destroy]
  end

  relationships do
    belongs_to :reactant, Flame.App.Resources.Reactant, primary_key?: true, allow_nil?: false
    belongs_to :source, Flame.App.Resources.Source, primary_key?: true, allow_nil?: false
  end
...
end
If I create a new Reactant as follows. 
    {:ok, reactant} = Flame.App.Resources.Reactant
    |> Ash.Changeset.new(%{identity: "test_reactant"})
    |> Ash.Changeset.for_create(:define, %{
      source_definitions: [%{description: "earth"}, %{description: "space"}]
    })
    |> Flame.App.create()
    {:ok, reactant} = Flame.App.Resources.Reactant
    |> Ash.Changeset.new(%{identity: "test_reactant"})
    |> Ash.Changeset.for_create(:define, %{
      source_definitions: [%{description: "earth"}, %{description: "space"}]
    })
    |> Flame.App.create()
It works and creates a Reactant while creating and relating two Sources. If I then update the reactant as follows. 
  reactant =
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: nil})
    |> Flame.App.update()
  reactant =
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: nil})
    |> Flame.App.update()
This also works unrelating both Sources without destroying the Sources from their table. Then if I update the reactant as below. 
  reactant = 
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: [%{description: "earth"}] })
    |> Flame.App.update()
  reactant = 
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: [%{description: "earth"}] })
    |> Flame.App.update()
This works as expected relating the existing Source from its table without creating a new Source. But the following two updates fail after this update. 
  reactant =
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: [%{description: "earth"}, %{description: "mars"}] })
    |> Flame.App.update()
# OR
  reactant =
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: [%{description: "earth"}, %{description: "space"}] })
    |> Flame.App.update()
  reactant =
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: [%{description: "earth"}, %{description: "mars"}] })
    |> Flame.App.update()
# OR
  reactant =
    reactant
    |> Ash.Changeset.for_update(:redefine, %{source_definitions: [%{description: "earth"}, %{description: "space"}] })
    |> Flame.App.update()
The error suggests its trying to create an entry in the join resource ReactantSource which already exists.
ZachDaniel
ZachDaniel•2y ago
     change manage_relationship(:source_definitions, :sources,
               on_lookup: :relate,
               on_match: :update,
               on_no_match: :create,
               on_missing: :unrelate,
               use_identities: [:the_identity_on_description]
             )
     change manage_relationship(:source_definitions, :sources,
               on_lookup: :relate,
               on_match: :update,
               on_no_match: :create,
               on_missing: :unrelate,
               use_identities: [:the_identity_on_description]
             )
I believe what you need the the use_identities option so it knows to look it up by certain keys by default it only looks for priamry key matches
morfertaw
morfertawOP•2y ago
It works as expected now! I had incorrectly assumed that, by default, it would use all identities and if any matched, trigger the on_match.

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