AF
Ash Framework•4mo ago
Oliver

Using no attributes to use a parent_type / parent_id style table as a join table

I have this table: 
attributes do
    integer_primary_key :id

    attribute :target_type, Safari.Types.LithostratTargetType, public?: true, allow_nil?: false
    attribute :target_id, :integer, public?: true, allow_nil?: false
    create_timestamp :inserted_at, public?: true
    update_timestamp :updated_at, public?: true
  end

  relationships do
    belongs_to :parent, Safari.Outcrop.Outcrop, public?: true, allow_nil?: false

    has_one :group, Safari.Wiki.Group,
      source_attribute: :target_id,
      destination_attribute: :id,
      filter: expr(parent(target_type) == :group)

    has_one :formation, Safari.Wiki.Formation,
      source_attribute: :target_id,
      destination_attribute: :id,
      filter: expr(parent(target_type) == :formation)

    has_one :member, Safari.Wiki.Member,
      source_attribute: :target_id,
      destination_attribute: :id,
      filter: expr(parent(target_type) == :member)
  end
attributes do
    integer_primary_key :id

    attribute :target_type, Safari.Types.LithostratTargetType, public?: true, allow_nil?: false
    attribute :target_id, :integer, public?: true, allow_nil?: false
    create_timestamp :inserted_at, public?: true
    update_timestamp :updated_at, public?: true
  end

  relationships do
    belongs_to :parent, Safari.Outcrop.Outcrop, public?: true, allow_nil?: false

    has_one :group, Safari.Wiki.Group,
      source_attribute: :target_id,
      destination_attribute: :id,
      filter: expr(parent(target_type) == :group)

    has_one :formation, Safari.Wiki.Formation,
      source_attribute: :target_id,
      destination_attribute: :id,
      filter: expr(parent(target_type) == :formation)

    has_one :member, Safari.Wiki.Member,
      source_attribute: :target_id,
      destination_attribute: :id,
      filter: expr(parent(target_type) == :member)
  end
And in Group I want to query all Outcrop through this table.. I thought I had done this before and I am currently stuck here (in relationships of Group): 
has_many :outcrops, Outcrop do
      no_attributes? true
      filter expr(what_to_put_here.target_id == parent(id) and target_type == :group)
    end
has_many :outcrops, Outcrop do
      no_attributes? true
      filter expr(what_to_put_here.target_id == parent(id) and target_type == :group)
    end
Solution:
Ok for anyone else coming across this post because they want to use no_attributes? true to do some complex mapping, here is the gist of it: - You can do a has_many or has_one to any App.Domain.Resource with some prereqs: - There must be a tangible path mapped up back to what you want - In my case I had...
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4 Replies
Oliver
OliverOP•4mo ago
I guess I need to put in another relationship in the Group resource that points at the join table to replace the what_to_put_here This is a little bit closer, but it is also not a way to get actual Outcrop out 😄 
has_many :outcrops, Outcrop do
      no_attributes? true
      filter expr(lithostrat_outcrop_links.target_id == parent(id) and target_type == :group)
    end

    has_many :lithostrat_outcrop_links, Safari.Wiki.LithostratOutcropLink,
      source_attribute: :id,
      destination_attribute: :target_id,
      filter: expr(target_type == :group)
has_many :outcrops, Outcrop do
      no_attributes? true
      filter expr(lithostrat_outcrop_links.target_id == parent(id) and target_type == :group)
    end

    has_many :lithostrat_outcrop_links, Safari.Wiki.LithostratOutcropLink,
      source_attribute: :id,
      destination_attribute: :target_id,
      filter: expr(target_type == :group)
the bottom one is the correct way to map up the link to the lithostrat outcrop link table at least how to utilize it as a join table to get outcrops? maybe better to set up a calc to do that? My goal here is that I want to expose group.outcrops{..} on the graphql side of things
ZachDaniel
ZachDaniel•4mo ago
You can have paths in parent expr(parent(through.thing_id) == ...) does that help?
Oliver
OliverOP•4mo ago
Does that help me select the outcrop? I will iterate a little here
Solution
Oliver
Oliver•4mo ago
Ok for anyone else coming across this post because they want to use no_attributes? true to do some complex mapping, here is the gist of it: - You can do a has_many or has_one to any App.Domain.Resource with some prereqs: - There must be a tangible path mapped up back to what you want - In my case I had - Outcrop - LithostratOutcropLink (with parent_id == outcrop, target_type == group|member|formation and target_id == the id of the group etc) - Group Solution to put on Group: 
has_many :outcrops, Safari.Outcrop.Outcrop do
      no_attributes? true

      filter expr(
               lithostrat_outcrop_links.target_id == parent(id) and
                 lithostrat_outcrop_links.target_type == :group
             )
    end
has_many :outcrops, Safari.Outcrop.Outcrop do
      no_attributes? true

      filter expr(
               lithostrat_outcrop_links.target_id == parent(id) and
                 lithostrat_outcrop_links.target_type == :group
             )
    end
This works because outcrop has: 
has_many :lithostrat_outcrop_links, LithostratOutcropLink,
      public?: true,
      destination_attribute: :parent_id
has_many :lithostrat_outcrop_links, LithostratOutcropLink,
      public?: true,
      destination_attribute: :parent_id
And that lets the filter traverse this relation and relate the ids etc with the source resource, using this middle table as an impromptu jointable.

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