Refactor survey response loader to use functional style

app/services/survey_responses_data_loader.rb

@@ -1,10 +1,8 @@
 require 'csv'
 
 class SurveyResponsesDataLoader
-  @@survey_item_responses = []
 
   def self.load_data(filepath:)
-    @@survey_item_responses = []
     csv_file = File.read(filepath)
 
     parsed_csv_file = CSV.parse(csv_file, headers: true)
@@ -13,11 +11,11 @@ class SurveyResponsesDataLoader
                          .filter { |header| header.start_with? 't-' or header.start_with? 's-' }
                          .map { |survey_item_id| SurveyItem.find_by_survey_item_id survey_item_id }
 
-    parsed_csv_file.each do |row|
+    survey_item_responses = parsed_csv_file.map do |row|
       process_row row: row, survey_items: survey_items
     end
 
-    SurveyItemResponse.import @@survey_item_responses
+    SurveyItemResponse.import survey_item_responses.compact.flatten
   end
 
   private
@@ -35,20 +33,20 @@ class SurveyResponsesDataLoader
     school = School.find_by_district_code_and_school_code(district_code, school_code)
     return if school.nil?
 
-    survey_items.each do |survey_item|
-      return unless SurveyItemResponse.find_by(response_id: response_id, survey_item: survey_item).nil?
+    survey_items.map do |survey_item|
+      next unless SurveyItemResponse.find_by(response_id: response_id, survey_item: survey_item).nil?
 
       likert_score = row[survey_item.survey_item_id]
       next if likert_score.nil?
-      @@survey_item_responses << SurveyItemResponse.new(
+
+      SurveyItemResponse.new(
         response_id: response_id,
         academic_year: academic_year,
         school: school,
         survey_item: survey_item,
         likert_score: likert_score
       )
-    end
-
+    end.compact
   end
 
 end