AE
Ash Elixir•2y ago
Emad Shaaban

How to insert a record with its nested children?

First, I'd love to thank everyone and especially Zash for the awesome work done in Ash I have a few resources with some relationships between them, for brevity I'll only copy the relevant parts 
defmodule Example.Orders.Order do
  use Ash.Resource

  attributes do
    uuid_primary_key :id
    attribute :state, :atom, allow_nil?: false
  end

  relationships do
    has_many :lines, Example.Orders.OrderLine 
  end
end
defmodule Example.Orders.Order do
  use Ash.Resource

  attributes do
    uuid_primary_key :id
    attribute :state, :atom, allow_nil?: false
  end

  relationships do
    has_many :lines, Example.Orders.OrderLine 
  end
end
defmodule Example.Orders.OrderLine do
  use Ash.Resource

  attributes do
    uuid_primary_key :id
    attribute :quantity, :decimal, allow_nil?: false
  end

  relationships do
    belongs_to :order, Example.Orders.Order

    belongs_to :product, Example.Products.Product do
      api Example.Products
      allow_nil? false
      attribute_writable? true
    end
  end
end
defmodule Example.Orders.OrderLine do
  use Ash.Resource

  attributes do
    uuid_primary_key :id
    attribute :quantity, :decimal, allow_nil?: false
  end

  relationships do
    belongs_to :order, Example.Orders.Order

    belongs_to :product, Example.Products.Product do
      api Example.Products
      allow_nil? false
      attribute_writable? true
    end
  end
end
What I wish to do is to insert an order along with its lines like this 
Example.Orders.Order.create!(%{
  state: :draft,
  lines: [%{
    product_id: ...,
    quantity: ...
  }]
})
Example.Orders.Order.create!(%{
  state: :draft,
  lines: [%{
    product_id: ...,
    quantity: ...
  }]
})
I could make it using manage_relationship, but it seems to require lines to be sent as an argument to the create action and not as a part of the order itself. I also tried Ash.Resource.Change like this 
defmodule Example.Orders.Order.Changes.SetLines do
  use Ash.Resource.Change

  def change(changeset, _, _) do
    lines = Ash.Changeset.get_attribute(changeset, :lines)

    changeset
    |> Ash.Changeset.manage_relationship(
      :lines,
      lines,
      type: :direct_control
    )
  end
end
defmodule Example.Orders.Order.Changes.SetLines do
  use Ash.Resource.Change

  def change(changeset, _, _) do
    lines = Ash.Changeset.get_attribute(changeset, :lines)

    changeset
    |> Ash.Changeset.manage_relationship(
      :lines,
      lines,
      type: :direct_control
    )
  end
end
elixir And updated the create action in order resource to be like this 
create :create do
  change Example.Orders.Order.Changes.SetLines
end
create :create do
  change Example.Orders.Order.Changes.SetLines
end
but it doesn't work, and it seems that :lines always get removed from changeset before the change code runs. Am I missing something? I don't mind sending lines as an argument to the action in this case, but then what happens with multiple levels of nesting?
2 Replies
ZachDaniel
ZachDaniel•2y ago
👋 So managed relationships is the way to accomplish this. Check out the docs for Ash.Changeset.manage_relationship (there is a lot there, sorry 😆 ). when managing relationships, we call actions on the destination resources based on the manage relationsh options. This defaults to the primary actions of a given type on a resource. Here is what you'd do 
efmodule Example.Orders.Order do
  use Ash.Resource
 
  actions do
    create :create do
      argument :lines, {:array, :map}
      change manage_relationship(:lines, type: :direct_control)
    end
  end

  ...
end
efmodule Example.Orders.Order do
  use Ash.Resource
 
  actions do
    create :create do
      argument :lines, {:array, :map}
      change manage_relationship(:lines, type: :direct_control)
    end
  end

  ...
end
That would let you do create(... %{attributes, ...., lines: [%{}, ...]}) and it will call teh relevant actions on OrderLine
Emad Shaaban
Emad ShaabanOP•2y ago
Thanks so much for the instant reply Zash, You keep amazing me I just tried it and it works well, I think I was almost there .. only needed to add the argument line in the create action. I feel dumb I didn't try that before asking 😦 I think what confused me is that I didn't expect manage_relationship to pick arguments from inside the main record :thinkies:, I used arguments for other actions and always sent them as extra parameters, maybe that's why.

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