example.rb

task :postcode_import => :environment do
  puts "\n\n Importing PostCodes"
 
  file = open("lib/data/example.csv")
  #gz = Zlib::GzipReader.new(file).read
  gz = CSV.read(file)
  arr = []
  gz.each do |line|
    arr << line
  end
  
  new_arr = arr.map { |a| a.split(',') }
  lat_long_res = []
  new_arr.each do |row|
    postcode = row[0]
    postcode.each {|x| x.scan(/.{4}|.+/).join(' ')} #Insert a space after the 4 character
    easting = row[1].to_i
    northing = row[2].to_i
    en_to_ll = Silva::Location.from(:en, :easting => easting, :northing => northing).to(:wgs84)
    lat_long_res << en_to_ll
    #lat_long_res << postcode
  end
  lat_long_res.flatten
  lat_long_res.each { |lat, long| Postcode.first_or_create(lat: lat, long: long)}
  #lat_long_res.each {|postcode,lat, long| Postcode.find_or_create_by(postcode: postcode, lat: lat, long: long)}
end

example_postcodes

AB106XB #This here doesn't have a space

CB2 1EG # This here has a space. 

Sample data

CB114XJ,548574,239518
CB114XL,548294,240759
CB114XN,546017,237185
CB114XU,551586,239676
CB114YR,553692,238424
CB114ZH,553578,237976
CB114ZX,553692,238424
CB2 0AA,546031,254843
CB2 0AB,546317,255439
CB2 0AD,546284,255443
CB2 0AE,546251,255443
CB2 0AF,546218,255447