Add graphql object types

app/graphql/loaders/association.rb

@@ -0,0 +1,66 @@
+# references:
+# https://github.com/Shopify/graphql-batch/blob/master/examples/association_loader.rb
+# https://gist.github.com/palkan/03eb5306a1a3e8addbe8df97a298a466
+# https://evilmartians.com/chronicles/active-storage-meets-graphql-pt-2-exposing-attachment-urls
+
+module Loaders
+  class Association < GraphQL::Batch::Loader
+    def self.validate(model, association_name)
+      new(model, association_name)
+      nil
+    end
+
+    def initialize(model, association_schema)
+      @model = model
+      @association_schema = association_schema
+      @association_name = extract_association_id(association_schema)
+      validate
+    end
+
+    def load(record)
+      raise TypeError, "#{@model} loader can't load association for #{record.class}" unless record.is_a?(@model)
+      return Promise.resolve(read_association(record)) if association_loaded?(record)
+      super
+    end
+
+    # We want to load the associations on all records, even if they have the same id
+    def cache_key(record)
+      record.object_id
+    end
+
+    def perform(records)
+      preload_association(records.uniq)
+      records.each { |record| fulfill(record, read_association(record)) }
+    end
+
+    private
+
+    def validate
+      unless @model.reflect_on_association(@association_name)
+        raise ArgumentError, "No association #{@association_name} on #{@model}"
+      end
+    end
+
+    def preload_association(records)
+      ::ActiveRecord::Associations::Preloader.new.preload(records, @association_schema)
+    end
+
+    def read_association(record)
+      record.public_send(@association_name)
+    end
+
+    def association_loaded?(record)
+      record.association(@association_name).loaded?
+    end
+
+    def extract_association_id(id_or_hash)
+      return id_or_hash unless id_or_hash.is_a?(Hash)
+
+      if id_or_hash.keys.size != 1
+        raise ArgumentError, "You can only preload exactly one association! You passed: #{id_or_hash}"
+      end
+
+      id_or_hash.keys.first
+    end
+  end
+end

app/graphql/loaders/record.rb

@@ -0,0 +1,30 @@
+# references:
+# https://github.com/Shopify/graphql-batch/blob/master/examples/record_loader.rb
+
+module Loaders
+  class Record < GraphQL::Batch::Loader
+    def initialize(model, column: model.primary_key, where: nil)
+      @model = model
+      @column = column.to_s
+      @column_type = model.type_for_attribute(@column)
+      @where = where
+    end
+
+    def load(key)
+      super(@column_type.cast(key))
+    end
+
+    def perform(keys)
+      query(keys).each { |record| fulfill(record.public_send(@column), record) }
+      keys.each { |key| fulfill(key, nil) unless fulfilled?(key) }
+    end
+
+    private
+
+    def query(keys)
+      scope = @model
+      scope = scope.where(@where) if @where
+      scope.where(@column => keys)
+    end
+  end
+end