AE
Ash Elixir•2y ago
Stefan Wintermeyer

How to create a product with a category id?

The setup: lib/app/shop/resources/category.ex 
defmodule App.Shop.Category do
  use Ash.Resource, data_layer: Ash.DataLayer.Ets

  attributes do
    uuid_primary_key :id
    attribute :name, :string
  end

  actions do
    defaults [:create, :read]
  end

  code_interface do
    define_for App.Shop
    define :create
    define :read
  end
end
defmodule App.Shop.Category do
  use Ash.Resource, data_layer: Ash.DataLayer.Ets

  attributes do
    uuid_primary_key :id
    attribute :name, :string
  end

  actions do
    defaults [:create, :read]
  end

  code_interface do
    define_for App.Shop
    define :create
    define :read
  end
end
lib/app/shop/resources/product.ex 
defmodule App.Shop.Product do
  use Ash.Resource, data_layer: Ash.DataLayer.Ets

  attributes do
    uuid_primary_key :id
    attribute :name, :string
    attribute :price, :decimal
  end

  relationships do
    belongs_to :category, App.Shop.Category
  end

  actions do
    defaults [:create, :read]
  end

  code_interface do
    define_for App.Shop
    define :create
    define :read
  end
end
defmodule App.Shop.Product do
  use Ash.Resource, data_layer: Ash.DataLayer.Ets

  attributes do
    uuid_primary_key :id
    attribute :name, :string
    attribute :price, :decimal
  end

  relationships do
    belongs_to :category, App.Shop.Category
  end

  actions do
    defaults [:create, :read]
  end

  code_interface do
    define_for App.Shop
    define :create
    define :read
  end
end
Question: How can I create a new Product which includes a Category? This is what I tried: 
iex(1)> fruits = App.Shop.Category.create!(%{name: "Fruits"})
#App.Shop.Category<
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "5b582e8a-3c19-4ce4-b609-88748a46e2ce",
  name: "Fruits",
  aggregates: %{},
  calculations: %{},
  ...
>
iex(3)> orange = App.Shop.Product.create!(%{name: "Orange", price: 0.20, category: fruits})
#App.Shop.Product<
  category: #Ash.NotLoaded<:relationship>,
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "432152d7-715d-4731-8fe4-ed90b05ee30e",
  name: "Orange",
  price: Decimal.new("0.2"),
  category_id: nil,
  aggregates: %{},
  calculations: %{},
  ...
>
iex(4)> orange = App.Shop.Product.create!(%{name: "Orange", price: 0.20, category_id: fruits.id})
#App.Shop.Product<
  category: #Ash.NotLoaded<:relationship>,
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "68c1023e-5b57-4819-a4a2-ff16f7efdc5d",
  name: "Orange",
  price: Decimal.new("0.2"),
  category_id: nil,
  aggregates: %{},
  calculations: %{},
  ...
>
iex(5)> 
iex(1)> fruits = App.Shop.Category.create!(%{name: "Fruits"})
#App.Shop.Category<
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "5b582e8a-3c19-4ce4-b609-88748a46e2ce",
  name: "Fruits",
  aggregates: %{},
  calculations: %{},
  ...
>
iex(3)> orange = App.Shop.Product.create!(%{name: "Orange", price: 0.20, category: fruits})
#App.Shop.Product<
  category: #Ash.NotLoaded<:relationship>,
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "432152d7-715d-4731-8fe4-ed90b05ee30e",
  name: "Orange",
  price: Decimal.new("0.2"),
  category_id: nil,
  aggregates: %{},
  calculations: %{},
  ...
>
iex(4)> orange = App.Shop.Product.create!(%{name: "Orange", price: 0.20, category_id: fruits.id})
#App.Shop.Product<
  category: #Ash.NotLoaded<:relationship>,
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "68c1023e-5b57-4819-a4a2-ff16f7efdc5d",
  name: "Orange",
  price: Decimal.new("0.2"),
  category_id: nil,
  aggregates: %{},
  calculations: %{},
  ...
>
iex(5)>
The category_id is nil both times.
9 Replies
kernel
kernel•2y ago
use manage_relationship 
actions do
  create :create do
    argument :category_id, :uuid
    change manage_relationship(:category_id, :category, type: :append_and_remove)
  end
end
actions do
  create :create do
    argument :category_id, :uuid
    change manage_relationship(:category_id, :category, type: :append_and_remove)
  end
end
roughly something like that ( i think you may have to swap the first two params in the manage_relationship)
kernel
kernel•2y ago
or directly on the changeset
No description
barnabasj
barnabasj•2y ago
If you wan't to set the id directly you need to make the attribute writeable https://ash-hq.org/docs/dsl/ash-resource#relationships-belongs_to-attribute_writable-
Ash HQ
Ash.Resource
View the documentation for Ash.Resource on Ash HQ.
Stefan Wintermeyer
Stefan WintermeyerOP•2y ago
What is the right syntax for that? https://ash-hq.org/docs/dsl/ash-resource#relationships-belongs_to-attribute_writable- doesn't contain an example. This doesn't work: 
  relationships do
    belongs_to :category, App.Shop.Category do
      writeable?: true
    end
  end
  relationships do
    belongs_to :category, App.Shop.Category do
      writeable?: true
    end
  end
barnabasj
barnabasj•2y ago
I think it should be attribute_writable? not just writeable? inside the do\end block you never have to use : 
  relationships do
    belongs_to :category, App.Shop.Category do
      attribute_writeable? true
    end
  end
  relationships do
    belongs_to :category, App.Shop.Category do
      attribute_writeable? true
    end
  end
Stefan Wintermeyer
Stefan WintermeyerOP•2y ago
Thanks @barnabasj! For the archive. Here's the fixed code and how it's working: 
  relationships do
    belongs_to :category, App.Shop.Category do
      attribute_writable? true
    end
  end
  relationships do
    belongs_to :category, App.Shop.Category do
      attribute_writable? true
    end
  end
iex(13)> orange = App.Shop.Product.create!(%{name: "Orange", price: 0.20, category_id: fruits.id})
#App.Shop.Product<
  category: #Ash.NotLoaded<:relationship>,
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "40cc21c2-58f8-4db4-8d98-7ab7c1741fa8",
  name: "Orange",
  price: Decimal.new("0.2"),
  category_id: "5b582e8a-3c19-4ce4-b609-88748a46e2ce",
  aggregates: %{},
  calculations: %{},
  ...
>
iex(13)> orange = App.Shop.Product.create!(%{name: "Orange", price: 0.20, category_id: fruits.id})
#App.Shop.Product<
  category: #Ash.NotLoaded<:relationship>,
  __meta__: #Ecto.Schema.Metadata<:loaded>,
  id: "40cc21c2-58f8-4db4-8d98-7ab7c1741fa8",
  name: "Orange",
  price: Decimal.new("0.2"),
  category_id: "5b582e8a-3c19-4ce4-b609-88748a46e2ce",
  aggregates: %{},
  calculations: %{},
  ...
>
This doesn't work: 
App.Shop.Product.create!(%{name: "Orange", price: 0.20, category: fruits})
App.Shop.Product.create!(%{name: "Orange", price: 0.20, category: fruits})
Should it but I configured the resource wrong or shouldn't it never because this isn't ActiveRecord?
barnabasj
barnabasj•2y ago
No it shouldn't work out of the box. If you wan't that you need to use manage_relationship like kernel suggested
Stefan Wintermeyer
Stefan WintermeyerOP•2y ago
@barnabasj Since I am writing beginners documentation I'd like to know if I understand it right: Code like App.Shop.Product.create!(%{name: "Orange", price: 0.20, category: %{name: "Fruits"}} is not the Ash way or is it? I am not so much interested in what is possible by opening all escape hatches but what is the intended way of doing it. I have one new Category and I have one new Product. What is the fastest way of creating it? What is the Ash way of doing it?
barnabasj
barnabasj•2y ago
I think both ways are equally valid and Ash just doesn't assume what you want. You have to be more explicit by telling ash how you would like to manage your relationships I use both ways in my code. Depending on the life-cycle of the resources and which resource I want to manage the relationship and so on.

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