Import graphs including anonymous objects

lib/data_food_consortium/connector/importer.rb

@@ -14,7 +14,11 @@ module DataFoodConsortium
 
       def self.type_map
         @type_map ||= TYPES.each_with_object({}) do |clazz, result|
-          type_uri = clazz.new(nil).semanticType
+          # Methods with variable arguments have a negative arity of -n-1
+          # where n is the number of required arguments.
+          number_of_required_args = -1 * (clazz.instance_method(:initialize).arity + 1)
+          args = Array.new(number_of_required_args)
+          type_uri = clazz.new(*args).semanticType
           result[type_uri] = clazz
         end
       end
@@ -48,11 +52,12 @@ module DataFoodConsortium
       end
 
       def build_subject(type_statement)
-        id = type_statement.subject.value
+        # Not all subjects have an id, some are anonymous.
+        id = type_statement.subject.try(:value)
         type = type_statement.object.value
         clazz = self.class.type_map[type]
 
-        clazz.new(id)
+        clazz.new(*[id].compact)
       end
 
       def apply_statements(statements)

spec/lib/data_food_consortium/connector/importer_spec.rb

@@ -31,6 +31,18 @@ describe DataFoodConsortium::Connector::Importer, vcr: true do
       name: "Ocra",
     )
   end
+  let(:quantity) do
+    DataFoodConsortium::Connector::QuantitativeValue.new(
+      unit: piece,
+      value: 5,
+    )
+  end
+  let(:piece) do
+    unless connector.MEASURES.respond_to?(:UNIT)
+      connector.loadMeasures(read_file("measures"))
+    end
+    connector.MEASURES.UNIT.QUANTITYUNIT.PIECE
+  end
 
   it "imports a single object with simple properties" do
     result = import(product)
@@ -59,6 +71,18 @@ describe DataFoodConsortium::Connector::Importer, vcr: true do
     expect(tomato.totalTheoreticalStock).to eq 3
   end
 
+  it "imports a graph including anonymous objects" do
+    product.quantity = quantity
+
+    tomato, items = import(product)
+
+    expect(tomato.name).to eq "Tomato"
+    expect(items.value).to eq 5
+
+    # Pending matching concepts:
+    #expect(items.unit).to eq piece
+  end
+
   it "imports properties with lists" do
     result = import(enterprise, product, second_product)
 
@@ -73,4 +97,10 @@ describe DataFoodConsortium::Connector::Importer, vcr: true do
     json = connector.export(*args)
     connector.import(json)
   end
+
+  def read_file(name)
+    JSON.parse(
+      Rails.root.join("engines/dfc_provider/vendor/#{name}.json").read
+    )
+  end
 end