by sandipransing
1.Install geokit gem
gem install geokit
OR
# Add following line inside rails initialize block
Rails::Initializer.run do |config|
config.gem 'geokit'
end
And then run command
rake gems:install
2. Consider User model with zipcode as attribute field
include Geokit::Geocoders
class User < ActiveRecord::Base
set_table_name :users
validate_presence_of :zipcode
validate :request_zipcode_validation_using_geokit, :if => :zipcode
private
def request_zipcode_validation_using_geokit
# Method request google api for location
# if location found then zipcode is valid otherwise
# add validation error on zipcode field
# as it method contacts with google api and takes time
# to return result, poll request only when zipcode gets
# changed
poll = true # default true for new objects
if self.id ## this means already existing user and zipcode is valid last time
# Hack to find where zipcode got modified or not
# old_user = User.find self.id
poll = false if old_user.zipcode == self.zipcode
end
# Actual requesting api to return location associated with zipcode
if poll
loc = MultiGeocoder.geocode(self.zip_code)
end
# Add Validation Error if location is not found
errors.add(:zip_code, "Unable to geocode your location from zipcode entered.") unless loc.success
end
Please note that same method can also be used to validate state, city and country.
Again we can use combination of fields to validate each other.
Like -
1. Based on country entered, state validation
2. Based on state, city validation
3. Based on city, zipcode validation
or
4. Based on zipcode and country, state and city validation
Here is another method to validate state and city based on zipcode and country.
Lets take example of 'US'
def request_state_and_city_validation_based_on_zipcode
poll = true # default true for new objects
if self.id ## this means already existing user and all attributes were valid last time
# Hack to find any one of location attribute got modified
# old_user = User.find self.id
loc_attrs = %w{zipcode state city} # keep in mind country US is default assumed
if loc_attrs.all? {|attr| self.attribute_for_inspect(attr) == old_user.attribute_for_inspect(attr)}
self.poll = false
end
end
# Actual requesting api to return location associated with zipcode
if poll
loc = MultiGeocoder.geocode("#{self.zip_code}, US")
end
# Add Validation Error if location is not found
unless loc.success
errors.add(:zip_code, "Unable to geocode your location from zipcode entered.")
else
# Validate state and city fields in compare to loc object returned by geocode
errors.add(:state, "State doesn't matches with zipcode entered") if self.state != loc.state
errors.add(:city, "City doesn't matches with zipcode entered") if self.city != loc.city
end
end
Note***
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Upcoming Posts
1. Geokit finders: Find locations in/within/beyond particular radius from specified location using acts_as_mappable plugin
2. Customizing authlogic for multiple sessions i.e. using different models for role based authentication.
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