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2d9f9ee362
note: these have been deprecated for a very long time, removing them will not be considered a breaking change (and there will be clear compile errors)
73 lines
2.3 KiB
Markdown
73 lines
2.3 KiB
Markdown
# Manual Actions
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Manual actions allow you to control how an action is performed instead of simply dispatching to a data layer. To do this, simply specify the `manual` option with a module that adopts the appropriate behavior. For example:
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Manual actions are a way to implement an action in a fully custom way. This can be a very useful escape hatch when you have something that you are finding difficult to model with Ash's builtin tools.
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## Manual Creates/Updates/Destroy
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For manual create/update/destroy actions, you will provide
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everything works pretty much the same, with the exception that the `after_action` hooks on a resource will receive a `nil` value for creates, and the old unmodified value for updates, and you are expected to add an after action hook that changes that `nil` value into the result of the action.
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For example:
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# in the action
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```elixir
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create :special_create do
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manual MyApp.DoCreate
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end
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# The change
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defmodule MyApp.DoCreate do
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use Ash.Resource.ManualCreate
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def create(changeset, _, _) do
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do_something_that_creates_the_record(changeset)
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end
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end
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```
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## Manual Read Actions
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Manual read actions work the same, except the will also get the "data layer query". For AshPostgres, this means you get the ecto query that would have been run.
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```elixir
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# in the resource
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actions do
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read :action_name do
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manual MyApp.ManualRead
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# or `{MyApp.ManualRead, ...opts}`
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end
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end
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# the implementation
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defmodule MyApp.ManualRead do
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use Ash.Resource.ManualRead
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def read(ash_query, ecto_query, _opts, _context) do
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...
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{:ok, query_results} | {:error, error}
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end
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end
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```
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### Modifying the query
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As an alternative to manual read actions, you can also provide the `modify_query` option, which takes an `MFA` and allows low level manipulation of the query just before it is dispatched to the data layer.
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For example:
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```elixir
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read :read do
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modify_query {MyApp.ModifyQuery, :modify, []}
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end
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defmodule MyApp.ModifyQuery do
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def modify(ash_query, data_layer_query) do
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{:ok, modify_data_layer_query(data_layer_query)}
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end
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end
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```
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This can be used as a last-resort escape hatch when you want to still use resource actions but need to do something that you can't do easily with Ash tools. As with any low level escape hatch, here be dragons.
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