feature: add common extractor

PC4-17243

lib/treasury/fields/extractor.rb

@@ -0,0 +1,42 @@
+module Treasury
+  module Fields
+    # Модуль добавляет классу метод extract_object, подходит для источников и полей денормализации.
+    #
+    # Example:
+    #
+    #   class Field
+    #     extend ::Treasury::Fields::Extractor
+    #     extract_attribute_name :user
+    #   end
+    #
+    #   Field.extract_object(object: {user_id: 1})
+    #     => 1
+    module Extractor
+      def extract_object(params)
+        object = params.fetch(:object)
+        object = object[attribute_name.to_sym] || object["#{attribute_name}_id".to_sym] if object.is_a?(Hash)
+
+        case object
+        when ::Numeric
+          object
+        when ::String
+          object.to_i
+        else
+          if object && object.respond_to?(:id)
+            object.id
+          else
+            raise ArgumentError,
+                  "#{attribute_name.capitalize} instance or Numeric/String #{attribute_name}_id expected!, "\
+                  "#{params.inspect}"
+          end
+        end
+      end
+
+      def extract_attribute_name(name)
+        class_attribute :attribute_name, instance_writer: false
+
+        self.attribute_name = name
+      end
+    end
+  end
+end

spec/lib/treasury/fields/extractor_spec.rb

@@ -0,0 +1,46 @@
+require 'spec_helper'
+
+RSpec.describe Treasury::Fields::Extractor do
+  let(:class_with_extractor) do
+    Class.new do
+      extend Treasury::Fields::Extractor
+
+      extract_attribute_name :user
+    end
+  end
+
+  describe '.extract_object' do
+    context 'when object key not present' do
+      it { expect { class_with_extractor.extract_object({}) }.to raise_error(KeyError) }
+    end
+
+    context 'when object_id not passed' do
+      it { expect { class_with_extractor.extract_object(object: {}) }.to raise_error(ArgumentError) }
+    end
+
+    context 'when object_id is nil' do
+      it { expect { class_with_extractor.extract_object(object: {user_id: nil}) }.to raise_error(ArgumentError) }
+    end
+
+    context 'when object is nil' do
+      it { expect { class_with_extractor.extract_object(object: nil) }.to raise_error(ArgumentError) }
+    end
+
+    context 'when extract another object' do
+      it { expect { class_with_extractor.extract_object(object: {another_object: 1}) }.to raise_error(ArgumentError) }
+    end
+
+    it 'return object id' do
+      user = double(:user, id: 1)
+
+      expect(class_with_extractor.extract_object(object: user)).to eq 1
+    end
+
+    it 'returns passed object_id' do
+      expect(class_with_extractor.extract_object(object: {user_id: 1})).to eq 1
+      expect(class_with_extractor.extract_object(object: {user_id: '1'})).to eq 1
+      expect(class_with_extractor.extract_object(object: {user: 1})).to eq 1
+      expect(class_with_extractor.extract_object(object: {user: '1'})).to eq 1
+    end
+  end
+end