Ash Elixir•3y ago

Bidirectional `manage_relationship`

Is there a way to get manage_relationship to manage the other side of the relationship simultaneously? Specifying destination_relationship: :other etc.

26 Replies

ZachDaniel•3y ago

manage_relationship calls actions on the destination resource, and by default those are the primary actions on the resource, but it can be changed by changing your options to manage_relationship (see the docs in Ash.Changeset module for manage_relationship. If you have those actions also call manage_relationship then they can do what they want

\ ឵឵឵OP•3y ago

Ok, so if my primary create action on the destination resource does something like:

actions do
  create :create do
    primary? true
    argument :other, App.Other
    change manage_relationship(:other, type: :append)
  end
end

actions do
  create :create do
    primary? true
    argument :other, App.Other
    change manage_relationship(:other, type: :append)
  end
end

How does it know which argument to provide to the related resource's create action?

ZachDaniel•3y ago

The input is provided nested

argument :relationship, :map

change manage_relationship(:relationship, ....)

%{relationship: %{other: %{a: 1}}}

argument :relationship, :map

change manage_relationship(:relationship, ....)

%{relationship: %{other: %{a: 1}}}

If the action on relationship managed :other

\ ឵឵឵OP•3y ago

This looks like it's for nested relationships.

ZachDaniel•3y ago

Ah, I guess I don't know what you mean about bidirectional then

\ ឵឵឵OP•3y ago

Populating the reverse relationship on the related resource.

ZachDaniel•3y ago

ah, I see. Nothing does that currently You can add an after_action hook to do it manually if you wanted That may or may not work

\ ឵឵឵OP•3y ago

other = %{id: Changeset.get_attribute(cs, :id)}

other = %{id: Changeset.get_attribute(cs, :id)}

ZachDaniel•3y ago

Could you show me a real example of what operation you're trying to do? and what you'd like to see returned for example

\ ឵឵឵OP•3y ago

Sure, sec This is how I'm doing it now, which works:

update :add_other do
  argument :other, :map

  change fn cs, r ->
    self = %{id: Changeset.get_attribute(cs, :id)}

    other =
      Changeset.get_argument(cs, :other)
      |> Map.put(:self, self)

    case App.Other.create(other) do
      {:ok, other} -> Changeset.manage_relationship(cs, :others, other, type: :create)
      err -> err
    end
  end
end

update :add_other do
  argument :other, :map

  change fn cs, r ->
    self = %{id: Changeset.get_attribute(cs, :id)}

    other =
      Changeset.get_argument(cs, :other)
      |> Map.put(:self, self)

    case App.Other.create(other) do
      {:ok, other} -> Changeset.manage_relationship(cs, :others, other, type: :create)
      err -> err
    end
  end
end

With the create action above on the target resource. Wondering if there's a shorthand to tell manage_relationsip to populate the relationship on the destination resource with the current resource, e.g. by providing the relationship name on the destination resource, or specifying it in the relationships section, e.g. reverse_relationship.

ZachDaniel•3y ago

Nothing to do that kind of thing automatically. So on the other resource, you have a manage_relationship call also? It seems like you'd just want to load that data, no need to manage it

\ ឵឵឵OP•3y ago

Currently, yes, for this method.

ZachDaniel•3y ago

update :add_other do
  argument :other, :map
  change manage_relationship(:other, :others, ...)
  
  change load(others: :self)  
end

update :add_other do
  argument :other, :map
  change manage_relationship(:other, :others, ...)
  
  change load(others: :self)  
end

\ ឵឵឵OP•3y ago

I think load doesn't inject the current resource on the destination?

ZachDaniel•3y ago

thats what the others: :self does using manage_relationship at all relates the destination things to the current thing you don't have to do that manually it just doesn't load the reverse relationship automatically

\ ឵឵឵OP•3y ago

If I don't add the current resource like this:

other =
      Changeset.get_argument(cs, :other)
      |> Map.put(:self, self)

other =
      Changeset.get_argument(cs, :other)
      |> Map.put(:self, self)

I was getting nil in the reverse relationship on the other resource.

ZachDaniel•3y ago

where were you getting nil? In the changeset?

\ ឵឵឵OP•3y ago

I'm not too worried about it loading the reverse relationship, just creating it. In the resulting created resources.

ZachDaniel•3y ago

🤔 you were getting nil, not %Ash.NotLoaded{}?

\ ឵឵឵OP•3y ago

Querying them after creation, the reverse relationship was nil.

ZachDaniel•3y ago

Sounds like potentially a misconfiguration of your relationship fields or something like that To debug further I think I'd need you to reproduce it in a test in ash

\ ឵឵឵OP•3y ago

    update :add_other do
      argument :other, :map
      change manage_relationship(:other, :others, type: :create)
    end

    update :add_other do
      argument :other, :map
      change manage_relationship(:other, :others, type: :create)
    end

So this should just work the way I was thinking, populating the current resource on the destination relationship during creation?

ZachDaniel•3y ago

yep! Thats the main purpose of manage_relationship is to create/update/destroy related things (and so creating them would imply making them related on creation) I'd check to make sure the reverse relationship isusing the right keys

\ ឵឵឵OP•3y ago

Great, I had the impression that this was how it was supposed to work 🙂 OOC is it required that there is an argument + manage_relationship call in the default create action of the destination resource?

ZachDaniel•3y ago

Nope @\ ឵឵឵ did you ever figure this one out?

\ ឵឵឵OP•3y ago

@Zach Daniel I believe so, but I didn't have time to dig into what was going wrong earlier. Tbh the behavior you described was what I was expecting at the start. If it crops up again I'll put together a minimal.

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