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102 lines
No EOL
2.7 KiB
Markdown
102 lines
No EOL
2.7 KiB
Markdown
# Define Idiomatic Actions
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The best practice is typically to try to push things as far down into your resources as possible.
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## The Non-idiomatic Way
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If you were doing a twitter front page, you might have a tweet resource with a simple action like this:
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```elixir
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# use a simple primary read
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defaults [:read, ...]
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```
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And in doing that, you could get all the tweets with something like this:
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```elixir
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Tweet
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|> Ash.Query.for_read(:read)
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|> Ash.Query.sort(posted_at: :desc)
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|> Ash.Query.filter(author.id == ^current_user.id or exists(author.friends, id == ^current_user.id))
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# assuming the name of your api was `Tweets`
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|> Tweets.read!()
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```
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And that works and in some cases might be the right way to do what you're trying to do
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And lets say there was a sort drop down that made it sort by popular instead of recent, you could do something like this:
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```elixir
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Tweet
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|> Ash.Query.for_read(:read)
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|> then(fn query ->
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case sort do
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:recent ->
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Ash.Query.sort(query, posted_at: :desc)
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:popular ->
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Ash.Query.sort(query, like_count: :desc)
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end
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end)
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|> Ash.Query.filter(author.id == ^current_user.id or exists(author.friends, id == ^current_user.id))
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# assuming the name of your api was `Tweets`
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|> Tweets.read!()
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```
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## The Idiomatic Way
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But the better way to model this would be something like this:
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```elixir
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code_interface do
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define_for MyApp.Tweets
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define :front_page, args: [:sort_by]
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end
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read :front_page do
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argument :sort_by, :atom do
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constraints one_of: [:recent, :popular]
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end
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prepare MyApp.Tweets.Tweet.Preparations.SortFrontPage
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filter expr(author.id == ^actor(:id) or exists(author.friends, id == ^actor(:id))
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end
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```
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Custom preparations allow you to do all sorts of things, in this case handle custom sorting
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```elixir
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defmodule MyApp.Tweets.Tweet.Preparations.SortFrontPage do
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use Ash.Resource.Preparation
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def prepare(query, _, _) do
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# We use `prepend?` to put the sort ahead of any other specified sort on the query
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case Ash.Changeset.get_argument(query, :sort_by) do
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:recent ->
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Ash.Query.sort(query, [posted_at: :desc], prepend?: true)
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:popular ->
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Ash.Query.sort(query, [like_count: :desc], prepend?: true)
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end
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end
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end
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```
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And then you can get the front page of tweets far more cleanly:
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```elixir
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Tweet.front_page!(socket.assigns.sort_by)
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```
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If you were using AshGraphql, you could do something like this:
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```elixir
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graphql do
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type :tweet
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queries do
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query :front_page, :front_page
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end
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end
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```
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And because you've made the action encompass the entire logic of fetching the front page, you've got automatic support for API access to your system.
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This is just one example of the benefits of having idiomatic and complete actions. |