add ash_tutorial
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ash_tutorial/attributes.livemd
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309
ash_tutorial/attributes.livemd
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# Ash: 4 - Attributes
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```elixir
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Application.put_env(:ash, :validate_domain_resource_inclusion?, false)
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Application.put_env(:ash, :validate_domain_config_inclusion?, false)
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Mix.install([{:ash, "~> 3.0"}], consolidate_protocols: false)
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```
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## Attributes
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<div class="flex items-center w-full flex-start justify-between rounded-xl p-4" style="background-color: #f0f5f9; color: #61758a;">
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<div class="flex">
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<i class="ri-arrow-left-fill"></i>
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<a class="flex ml-2" style="color: #61758a;" href="querying.livemd">Querying</a>
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</div>
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<div class="flex">
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<i class="ri-home-fill"></i>
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<a class="flex ml-2" style="color: #61758a;" href="overview.livemd">Home</a>
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</div>
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<div class="flex">
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<a class="flex mr-2" style="color: #61758a;" href="customizing_actions.livemd">Customizing Actions</a>
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<i class="ri-arrow-right-fill"></i>
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</div>
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</div>
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### In this tutorial you will add and configure Attributes to a Ticket resource
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The Ticket resource will represent a helpdesk ticket.
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It will have 3 main attributes.
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* A `subject` or title
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* A `description`
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* A `status` which can be either `:open` or `:closed`
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It will also have 2 attributes for keeping track of when the ticket was *created*, and when it was *last updated*.
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#### Subject
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You need to make sure the `subject` is always set, it's not possible to create a ticket without a subject. You can do this by setting `allow_nil?` to `false`. Like so: `attribute :subject, :string, allow_nil?: false`
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#### Description
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The `:description` is simple, it's a `:string` and it is allowed to be empty.
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#### Status
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`:status` is more complicated.
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* It is of the type `:atom`
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* It can only be the value `:open` or `:closed`
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* By default it is `:open`
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* And it can't be `nil`
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Attributes are set in a `do end` block like so:
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<!-- livebook:{"force_markdown":true} -->
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```elixir
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attribute :status, :atom do
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# ...
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allow_nil? false
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end
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```
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To set a constraint of values, you can use the `constraints` option, like so:
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`constraints [one_of: [:open, :closed]]`
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To set the default value, you use `default :open`.
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#### Keeping track of Created and Updated
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Ash provides [create_timestamp](https://hexdocs.pm/ash/dsl-ash-resource.html#attributes-create_timestamp) and [update_timestamp](https://hexdocs.pm/ash/dsl-ash-resource.html#attributes-update_timestamp) to keep track of when the Resource was first created, and when it was last updated.
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Add the following to the attributes block:
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<!-- livebook:{"force_markdown":true} -->
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```elixir
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create_timestamp :created_at
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update_timestamp :updated_at
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```
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<details class="rounded-lg my-4" style="background-color: #96ef86; color: #040604;">
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<summary class="cursor-pointer font-bold p-4"></i>Show Solution</summary>
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<div class="p-4">
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```elixir
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defmodule Tutorial.Support.Ticket do
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use Ash.Resource,
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domain: Tutorial.Support,
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data_layer: Ash.DataLayer.Ets
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actions do
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defaults [:read]
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create :create do
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accept [:subject, :description, :status]
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end
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end
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attributes do
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uuid_primary_key :id
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attribute :subject, :string, allow_nil?: false
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attribute :description, :string
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# status is either `open` or `closed`.
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attribute :status, :atom do
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# Constraints allow you to provide extra rules for the value.
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# The available constraints depend on the type
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# See the documentation for each type to know what constraints are available
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# Since atoms are generally only used when we know all of the values
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# it provides a `one_of` constraint, that only allows those values
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constraints [one_of: [:open, :closed]]
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default :open
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allow_nil? false
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end
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create_timestamp :created_at
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update_timestamp :updated_at
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end
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end
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defmodule Tutorial.Support do
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use Ash.Domain
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resources do
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resource Tutorial.Support.Ticket
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end
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end
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```
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</div>
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</details>
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### Enter your solution
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```elixir
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defmodule Tutorial.Support.Ticket do
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use Ash.Resource,
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domain: Tutorial.Support,
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data_layer: Ash.DataLayer.Ets
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actions do
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defaults [:read]
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create :create do
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accept [:subject, :description, :status]
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end
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end
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attributes do
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uuid_primary_key :id
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# Add the attributes here -->
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# - Subject
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# - Description
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# - Status
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# - Create Timestamp
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# - Update Timestamp
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end
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end
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defmodule Tutorial.Support do
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use Ash.Domain
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resources do
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resource Tutorial.Support.Ticket
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end
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end
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```
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## Creating a Ticket
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Create a `Ticket` without any attributes.
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Remember, when creating a resource use a changeset (`Ash.Changeset.for_create/3`), which gets passed to `Ash.create!/1`.
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The output should look something like this:
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```
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** (Ash.Error.Invalid) Input Invalid
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* attribute subject is required
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```
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<details class="rounded-lg my-4" style="background-color: #96ef86; color: #040604;">
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<summary class="cursor-pointer font-bold p-4"></i>Show Solution</summary>
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<div class="p-4">
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```elixir
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Tutorial.Support.Ticket
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|> Ash.Changeset.for_create(:create, %{})
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|> Ash.create!()
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```
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</div>
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</details>
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```elixir
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```
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Now create a Ticket with a `subject`
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<details class="rounded-lg my-4" style="background-color: #96ef86; color: #040604;">
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<summary class="cursor-pointer font-bold p-4"></i>Show Solution</summary>
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<div class="p-4">
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```elixir
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Tutorial.Support.Ticket
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|> Ash.Changeset.for_create(:create, %{subject: "This is the subject"})
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|> Ash.create!()
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```
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</div>
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</details>
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```elixir
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```
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Now create a ticket with the `status` set to `:closed`
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<details class="rounded-lg my-4" style="background-color: #96ef86; color: #040604;">
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<summary class="cursor-pointer font-bold p-4"></i>Show Solution</summary>
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<div class="p-4">
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```elixir
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Tutorial.Support.Ticket
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|> Ash.Changeset.for_create(:create, %{subject: "This is the subject", status: :closed})
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|> Ash.create!()
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```
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</div>
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</details>
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```elixir
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```
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Now try creating a ticket with the status set to `:pending`. This should give an error because `:pending` is not a valid `status`.
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<details class="rounded-lg my-4" style="background-color: #96ef86; color: #040604;">
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<summary class="cursor-pointer font-bold p-4"></i>Show Solution</summary>
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<div class="p-4">
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```elixir
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Tutorial.Support.Ticket
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|> Ash.Changeset.for_create(:create, %{subject: "This is the subject", status: :pending})
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|> Ash.create!()
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```
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</div>
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</details>
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```elixir
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```
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## Latest created Ticket
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Since you added a creation date, you can now query on the latest created ticket.
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First, sort using the `Ash.Query.sort/2` function by `Ash.Query.sort(created_at: :desc)`
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Then limit the amount of records with the `Ash.Query.limit/2` function by doing `Ash.Query.limit(1)`
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Finally call `Ash.read_one!()` on the query.
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*Hint: Use a pipeline*
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<details class="rounded-lg my-4" style="background-color: #96ef86; color: #040604;">
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<summary class="cursor-pointer font-bold p-4"></i>Show Solution</summary>
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<div class="p-4">
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```elixir
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Tutorial.Support.Ticket
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|> Ash.Query.sort(created_at: :desc)
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|> Ash.Query.limit(1)
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|> Ash.read_one!()
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```
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</div>
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</details>
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```elixir
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```
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<div class="flex items-center w-full flex-start justify-between rounded-xl p-4" style="background-color: #f0f5f9; color: #61758a;">
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<div class="flex">
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<i class="ri-arrow-left-fill"></i>
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<a class="flex ml-2" style="color: #61758a;" href="querying.livemd">Querying</a>
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</div>
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<div class="flex">
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||||
<i class="ri-home-fill"></i>
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<a class="flex ml-2" style="color: #61758a;" href="overview.livemd">Home</a>
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</div>
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<div class="flex">
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<a class="flex mr-2" style="color: #61758a;" href="customizing_actions.livemd">Customizing Actions</a>
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<i class="ri-arrow-right-fill"></i>
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</div>
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</div>
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