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docs: added changes guide docs: moved around validations guide, removed extra one
154 lines
5.8 KiB
Markdown
154 lines
5.8 KiB
Markdown
# Code Interface
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One of the ways that we interact with our resources is via hand-written code. The general pattern for that looks like building a query or a changeset for a given action, and calling it via functions like `Ash.read/2` and `Ash.create/2`. This, however, is just one way to use Ash, and is designed to help you build tools that work with resources, and to power things like `AshPhoenix.Form`, `AshGraphql.Resource` and `AshJsonApi.Resource`. When working with your resources in code, we generally want something more idiomatic and simple. For example, on a domain called `Helpdesk.Support`.
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```elixir
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resources do
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resource Ticket do
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define :open_ticket, args: [:subject], action: :open
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end
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end
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```
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This simple setup now allows you to open a ticket with `Helpdesk.Support.open_ticket(subject)`. You can cause it to raise errors instead of return them with `Helpdesk.Support.open_ticket!(subject)`. For information on the options and additional inputs these defined functions take, look at the generated function documentation, which you can do in iex with `h Helpdesk.Support.open_ticket`. For more information on the code interface, read the DSL documentation: `d:Ash.Domain.Dsl.resource.interfaces`.
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## Code interfaces on the resource
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You can define a code interface on individual resources as well, using the `code_interface` block. The DSL is the same as the DSL for defining it in the `domain`. For example:
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```elixir
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code_interface do
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# the action open can be omitted because it matches the functon name
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define :open, args: [:subject]
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end
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```
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These will then be called on the resource itself, i.e `Helpdesk.Support.Ticket.open(subject)`.
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## Using the code interface
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If the action is an update or destroy, it will take a record or a changeset as its _first_ argument.
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If the action is a read action, it will take a starting query as an _opt in the last_ argument.
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All functions will have an optional last argument that accepts options. See `Ash.Resource.Interface.interface_options/1` for valid options.
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For reads:
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- `:query` - a query to start the action with, can be used to filter/sort the results of the action.
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For creates:
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- `:changeset` - a changeset to start the action with
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They will also have an optional second to last argument that is a freeform map to provide action input. It _must be a map_.
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If it is a keyword list, it will be assumed that it is actually `options` (for convenience).
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This allows for the following behaviour:
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```elixir
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# Because the 3rd argument is a keyword list, we use it as options
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Accounts.register_user(username, password, [tenant: "organization_22"])
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# Because the 3rd argument is a map, we use it as action input
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Accounts.register_user(username, password, %{key: "val"})
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# When all arguments are provided it is unambiguous
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Accounts.register_user(username, password, %{key: "val"}, [tenant: "organization_22"])
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```
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## Calculations
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Resource calculations can be run dynamically using `Ash.calculate/3`, but
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you can also expose them using the code_interface with `define_calculation`.
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For example:
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```elixir
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calculations do
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calculate :full_name, :string, expr(first_name <> ^arg(:separator) <> last_name) do
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argument :separator, :string do
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allow_nil? false
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default " "
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end
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end
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end
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# in your domain
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resource User do
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define_calculation :full_name, args: [:first_name, :last_name, {:optional, :separator}]
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# or if you want to take a record as an argument
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define_calculation :full_name, args: [:_record]
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end
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```
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This could now be used like so:
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```elixir
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Accounts.full_name("Jessie", "James", "-")
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# or with a record as an argument
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Accounts.full_name(user)
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```
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This allows for running calculations without an instance of a resource, normally done via `Ash.load(user, :full_name)`
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By default, configured args will be provided for any matching named reference _or_ argument. This is normally fine, but in the case that you have an argument and a reference with the same name, you can specify it by supplying `{:arg, :name}` and `{:ref, :name}`. For example:
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```elixir
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define_calculation :id_matches, args: [{:arg, :id}, {:ref, :id}]
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```
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To make arguments optional, wrap them in `{:optional, ..}`, for example:
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```elixir
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define_calculation :id_matches, args: [{:arg, :id}, {:optional, {:ref, :id}}]
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```
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## Bulk & atomic actions
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### Bulk Updates & Destroys
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Updates support a list, stream, or query as the first argument. This allows for bulk updates. In this mode, an `%Ash.BulkResult{}` is returned.
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> ### Valid inputs {: .warning}
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>
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> You cannot provide "any enumerable", only lists, streams (a function or a %Stream{}), and queries. We have to be able to distinguish the input as a bulk input and not input to the action itself.
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For example:
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```elixir
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Post
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|> Ash.Query.filter(author_id == ^author_id)
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|> MyApp.Blog.archive_post!()
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# => %Ash.BulkResult{}
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[%Post{}, %Post{}]
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|> MyApp.Blog.destroy_post!()
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# => %Ash.BulkResult{}
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end
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```
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You can pass options to the bulk operation with the `bulk_options` option to your code interface function.
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### Bulk Creates
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For bulk creates, you can provide a list or stream of inputs. In this mode also, an `%Ash.BulkResult{}` is returned.
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> ### Valid inputs {: .warning}
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>
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> You cannot provide "any enumerable", only lists, streams (a function or a %Stream{}). We have to be able to distinguish the input as a bulk input and not input to the action itself.
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Any arguments on the code interface will be applied to _all_ inputs given as a list, and the arguments will come first.
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```elixir
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[%{title: "Post 1"}, %{title: "Post 2"}, ...]
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# if `:special` is an action argument, it will be applied to all inputs
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|> MyApp.Blog.create_post!(:special, bulk_options: [batch_size: 10])
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```
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### Returning streams from read actions
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The `:stream?` option allows you to return a stream to be enumerated later.
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For example:
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```elixir
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MyApp.Blog.my_posts(stream?: true, actor: me)
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# => #Stream<...>
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```
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