Geocode an address hash with Google geocode api

!Geocode an Address

I needed a tool to add latitude and longitude to seeds.rb in a Rails application.

geocoder.rb uses the Google geocode api. An apikey is required. For limited use it is free. The apikey should be protected from prying eyes. (encryption, .gitignore, ...)

Geocoder#geocode takes an address string in canonical form ( "#{number} #{street} #{city} #{state}" ) as input. It returns latitude and longitude as a hash: { lat: 30.0000, lng: -90.000 }

seed_geocoder.rb extracts the address string from seeds.rb, requests the geocode hash from the Geocoder obj and writes the newseeds.rb file. 

The newseeds file does need some minor additional work to make it a functional seeds.rb.

canonical_address.rb

class CanonicalAddress
  def initialize( city: 'Arlington', state: 'TX')
    @city = city
    @state = state
  end

  def strng(addr_hash)
    number = addr_hash.fetch('number')
    street = addr_hash.fetch('street')
    city   = addr_hash.fetch('city', @city)
    state  = addr_hash.fetch('state', @state)
    "#{number} #{street} #{city} #{state}"
  end

  def hsh(addr_hash)
    addr_hash.merge({city: @city, state: state})
  end
end

geocoder.rb

require 'json'
require 'httparty'

class Geocoder
  include HTTParty

  URL_GC = "https://maps.googleapis.com/maps/api/geocode/"

  attr_reader :url, :fmt, :keyfile

  def initialize( url: URL_GC, fmt: 'json', keyfile: 'apikey.txt')
    @url = url
    @fmt = fmt
    @keyfile = keyfile
  end

  def geocode(address)
    request = req(address)
    response = HTTParty.get(request)
    extract_coordinates(response)
  end

private
  def req(address)
    URL_GC+fmt+"?address=#{ address }&key= "#{ apikey }"
  end

  def extract_coordinates(response)
    JSON.parse(response.body)["results"].first["geometry"]["location"]
  end

  def apikey
    File.open(keyfile) {|f| key = f.read }
  end
end

newseeds.rb

[
  {"number"=>100, "street"=>"Howler Dr", "lat"=>31.0000000, "lng"=>-97.0000000},
  {"number"=>202, "street"=>"Johnson Ave", city: "Fort Worth", "lat"=>32.0000000, "lng"=>-97.0000000},
  {"number"=>303, "street"=>"Main St", city: "Dallas", state: "TX", "lat"=>32.0000000, "lng"=>-97.0000000},
]

runner.rb

require_relative 'seed_geocoder'

sg = SeedGeocoder.new( app:    '../wwna_roster',
                       matchr: %r{number: 6004} )
sg.geocode_seeds

seed_geocoder.rb

require 'yaml'
require_relative 'geocoder'
require_relative 'canonical_address'

class SeedGeocoder
  attr_reader :c_addr, :geocoder
  def initialize( app:    '../my_app',
                  src:    'db/seeds.rb',
                  dest:   'db/newseeds.rb',
                  matchr: %r{number:},
                  geocoder: Geocoder )
    @app = app
    @src = src
    @dest = dest
    @c_addr = CanonicalAddress.new
    @geocoder = geocoder.new
  end

  def geocode_seeds
    write(geocoded_seeds)
  end

private
  def write(seeds)
    return unless seeds
    File.open(dest, 'w') do |f|
      f.puts "[\n"
      seeds.each do |seed|
        f.puts "  #{seed.to_s},\n"
      end
      f.puts "]\n"
    end
  end

  def geocoded_seeds
    File.foreach(src).map do |line|
      next unless matchr =~ line
      addr = YAML.load(line)
      addr.merge geocoder.geocode(canonical addr)
    end.compact
  end

  def canonical(addr_hash)
    c_addr.strng(addr_hash)
  end

  def src
    @app + '/' + @src
  end

  def dest
    @app + '/' + @dest
  end
end

seeds.rb

# This file should contain all the record creation needed to seed the database with its default values.
# The data can then be loaded with the rails db:seed command (or created alongside the database with db:setup).
#
# Examples:
#
#   movies = Movie.create([{ name: 'Star Wars' }, { name: 'Lord of the Rings' }])
#   Character.create(name: 'Luke', movie: movies.first)

House.create([
  { number: 100, street: 'Howler Dr' },
  { number: 202, street: 'Johnson Ave', city: 'Fort Worth' },
  { number: 303, street: 'Main St', city: 'Dallas', state: 'TX' }
])