[temp][fix] Naive improvement for fetching many-to-one relations

exAspArk/batch-loader#5

README.md

@@ -18,6 +18,7 @@ This is a sample app which shows how Rails 5, ROM 4.0, GraphQL and Clean Archite
 - [x] modularization of fields in QueryType [app/graphql/query_type.rb](https://github.com/wmaciejak/rails_rom_graphql_clean_architecture_boilerplate/blob/master/app/graphql/query_type.rb#L6)
 - [x] Implementation of Clean Architecture
 - [x] Separation of seeds by the environment [db/seeds.rb](https://github.com/wmaciejak/rails_rom_graphql_clean_architecture_boilerplate/blob/master/db/seeds.rb)
+- [x] Loading relations one-to-many without N+1, fixed by naive implementation - [BatchLoader issue#5](https://github.com/exAspArk/batch-loader/issues/5)
 
 ## What's to be done
 
@@ -32,7 +33,6 @@ This is a sample app which shows how Rails 5, ROM 4.0, GraphQL and Clean Archite
 
 ## Known issues
 
-- [ ] [BatchLoader issue#5](https://github.com/exAspArk/batch-loader/issues/5) - Partly fixed by custom solution but it's still `in progress`
 - [ ] camelCase in queries(thx [RadoMark](https://github.com/RadoMark/))
 
 ## Links

app/graphql/types/post_type.rb

@@ -7,11 +7,10 @@
   field :title, !types.String
   field :created_at, !types.String
   field :updated_at, !types.String
-  field :comments, CommentType, resolve: ->(post, _, _) do
+  field :comments, types[CommentType], resolve: ->(post, _, _) do
     BatchLoader.for(post.id).batch do |post_ids, loader|
-      CommentRepo.new(ROM.env).all_for_posts(post_ids).each do |comment|
-        loader.call(comment.post_id, comment)
-      end
+      grouped_hash = CommentRepo.new(ROM.env).all_for_posts(post_ids).group_by(&:post_id)
+      post_ids.each { |post_id| loader.call(post_id, grouped_hash[post_id]) }
     end
   end
 end

app/graphql/types/user_type.rb

@@ -4,18 +4,16 @@
   name "User"
   field :email, types.String
   field :username, types.String
-  field :posts, PostType, resolve: ->(user, _, _) do
+  field :posts, types[PostType], resolve: ->(user, _, _) do
     BatchLoader.for(user.id).batch do |user_ids, loader|
-      PostRepo.new(ROM.env).all_for_user(user_ids).each do |post|
-        loader.call(post.user_id, post)
-      end
+      grouped_hash = PostRepo.new(ROM.env).all_for_user(user_ids).group_by(&:user_id)
+      user_ids.each { |user_id| loader.call(user_id, grouped_hash[user_id]) }
     end
   end
-  field :comments, CommentType, resolve: ->(user, _, _) do
-    BatchLoader.for(user.id).batch do |user_ids, loader|
-      CommentRepo.new(ROM.env).all_for_author(user_ids).each do |comment|
-        loader.call(comment.author_id, comment)
-      end
+  field :comments, types[CommentType], resolve: ->(user, _, _) do
+    BatchLoader.for(user.id).batch do |author_ids, loader|
+      grouped_hash = CommentRepo.new(ROM.env).all_for_author(author_ids).group_by(&:author_id)
+      author_ids.each { |author_id| loader.call(author_id, grouped_hash[author_id]) }
     end
   end
 end