mirror of
https://github.com/ash-project/ash.git
synced 2024-09-20 21:43:02 +12:00
62 lines
2.3 KiB
Markdown
62 lines
2.3 KiB
Markdown
# Define Manual Relationships
|
|
|
|
Manual relationships allow you to express complex or non-typical relationships between resources in a standard way.
|
|
Individual data layers may interact with manual relationships in their own way, so see their corresponding guides.
|
|
|
|
By default, the only thing manual relationships support is being loaded.
|
|
|
|
## Example
|
|
|
|
In our Helpdesk example, we'd like to have a way to find tickets
|
|
|
|
In the `Rep?` resource, define a `has_many` relationship as `manual` and point to the module where
|
|
it will be implemented.
|
|
|
|
```elixir
|
|
relationships do
|
|
has_many :tickets_above_threshold, Helpdesk.Support.Ticket do
|
|
manual Helpdesk.Support.Ticket.Relationships.TicketsAboveThreshold
|
|
end
|
|
end
|
|
```
|
|
|
|
Using Ash to get the destination records is ideal, so you can authorize access like normal
|
|
but if you need to use a raw ecto query here, you can. As long as you return the right structure.
|
|
|
|
The `TicketsAboveThreshold` module is implemented as follows.
|
|
|
|
```elixir
|
|
defmodule Helpdesk.Support.Ticket.Relationships.TicketsAboveThreshold do
|
|
use Ash.Resource.ManualRelationship
|
|
require Ash.Query
|
|
|
|
def load(records, _opts, %{query: query, actor: actor, authorize?: authorize?}) do
|
|
# Use existing records to limit resultds
|
|
rep_ids = Enum.map(records, & &1.id)
|
|
|
|
{:ok,
|
|
query
|
|
|> Ash.Query.filter(representative_id in ^rep_ids)
|
|
|> Ash.Query.filter(priority > representative.priority_threshold)
|
|
|> Helpdesk.Support.read!(actor: actor, authorize?: authorize?)
|
|
# Return the items grouped by the primary key of the source, i.e representative.id => [...tickets above threshold]
|
|
|> Enum.group_by(& &1.representative_id)}
|
|
end
|
|
end
|
|
```
|
|
|
|
## Using the Query
|
|
|
|
Since you likely want to support things like filtering your relationship when being loaded, you will want to make sure that you use the query being provided. However, depending on how you're loading the relationship, you may need to do things like fetch extra records. To do this, you might do things like
|
|
|
|
```elixir
|
|
def load(records, _opts, %{query: query, ..}) do
|
|
# unset some fields
|
|
fetch_query = Ash.Query.unset(query, [:limit, :offset])
|
|
|
|
# or, to be more safe/explicit, you might make a new query, explicitly setting only a few fields
|
|
fetch_query = query.resource |> Ash.Query.filter(^query.filter) |> Ash.Query.sort(query.sort)
|
|
|
|
...
|
|
end
|
|
```
|