ah_lecture_notes_01-20-2015

ah_lecture_notes.rb

require 'csv'
class ConfPanel < ActiveRecord::Base
  validates :code, presence: true
  validates :name, presence: true

  def self.import_from_csv(csv_file)
    ConfPanel.transaction do
      ConfPanel.destroy_all

      # Parse CSV content
      file = File.open(csv_file,'r:windows-1251:utf-8').read
      content = CSV.parse(file)

      # File.read returns a big string of the data in the csv file being read.
      # 'r:windows-1251:utf-8'  handles the conversion of windows to utf-8 encoding
      # CSV.parse restructures the big string into an array data structure one row at a time.


      # Check content:
      if content.blank?
        raise 'Empty conf_panels.csv file'
      end

      # Extract header
      header = content.shift.compact.map do |h|
        h.parameterize.underscore.to_sym
      end
      # shift = removes first element in the array, returns it, and "shifts" all other elements down by one
      # compact = removes nil values from the array
      # map = invokes given blck once for each element.  Creates new array containing the values returned by the block
      # parameterize:
      # => space becomes dash (-)
      # => comma becomes dash (-)
      # => letters get lowercased
      # => comma followed by space becomes single dash (-)
      # => parenthesis are removed
      # => periods are replaced with single dash (-)


      # Get elements row index.  (based on header index)
      # index = Returns the index of the first object in array such that the object is == to obj.

      code_index = header.index(:code)
      name_index = header.index(:name)
      standard_profile_index = header.index(:standard_profile)
      specimen_source_index = header.index(:specimen_source)
      test_type_index = header.index(:test_type)
      confirm_negative_index = header.index(:confirm_negative)

      content.each do |row|
        next if row.compact.empty?
        source_attributes = {
          code: row[code_index].to_s.strip,
          name: row[name_index].to_s.strip,
          standard_profile: row[standard_profile_index].to_s.strip,
          specimen_source: row[specimen_source_index].to_s.strip,
          test_type: row[test_type_index].to_s.strip,
          confirm_negative: row[confirm_negative_index].to_s.strip
        } # we're building a hash which will save row by row to the table
        ConfPanel.create!(source_attributes) # save this row.
        print '.'
      end
      puts 'Import complete'

    end

  end

  def self.export_to_csv(csv_file)
    CSV.open(csv_file, 'w') do |csv_row|
      csv_row << ["code", "name","standard_profile","specimen_source","test_type","confirm_negative"]

      # ConfPanel.where("test_type = 'Other'").each do |db_row|
      ConfPanel.all.each do |db_row|
        # csv_row << db_row.attributes.values  # this dumps ALL fields
        csv_row << [db_row.attributes["code"],
                   "#{db_row.attributes["name"]}",
                   db_row.attributes["standard_profile"],
                   db_row.attributes["specimen_source"],
                   db_row.attributes["test_type"],
                   db_row.attributes["confirm_negative"]]

        print '*'
      end

    end
    puts 'Export Complete'
  end

end