error running a scrape command ruby on rails - api

Question

I am trying to re-setup my app on a new computer and run a scrape to build the DB. When I run my first rake scraper:scrape, this is the error I am getting. I am not sure why I am getting this error any help would make my day.. cheers!
Art West#ARTWESTIV ~/desktop/duckduckjeep-master
$ rake scraper:scrape --trace
** Invoke scraper:scrape (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute scraper:scrape
rake aborted!
NoMethodError: undefined method `value' for nil:NilClass
c:/Users/Art West/desktop/duckduckjeep-master/lib/tasks/scraper.rake:17:in `block (3 levels) in <top (required)>'
c:/Users/Art West/desktop/duckduckjeep-master/lib/tasks/scraper.rake:12:in `loop'
c:/Users/Art West/desktop/duckduckjeep-master/lib/tasks/scraper.rake:12:in `block (2 levels) in <top (required)>'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/task.rb:240:in `call'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/task.rb:240:in `block in execute'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/task.rb:235:in `each'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/task.rb:235:in `execute'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/task.rb:165:in `invoke'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:150:in `invoke_task'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:106:in `each'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:106:in `block in top_level'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:115:in `run_with_threads'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:100:in `top_level'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:78:in `block in run'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:176:in `standard_exception_handling'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/lib/rake/application.rb:75:in `run'
c:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rake-10.4.2/bin/rake:33:in `<top (required)>'
c:/RailsInstaller/Ruby2.1.0/bin/rake:23:in `load'
c:/RailsInstaller/Ruby2.1.0/bin/rake:23:in `<main>'
Tasks: TOP => scraper:scrape
here is my scraper.rake
namespace :scraper do
desc "Fetch Craigslist posts from 3Taps"
task scrape: :environment do
require 'open-uri'
require 'json'
# Set API token and URL
auth_token = "b077632d17da8857e2fa92c053115e43"
polling_url = "http://polling.3taps.com/poll"
# Grab data until up-to-date
loop do
# Specify request parameters
params = {
auth_token: auth_token,
anchor: Anchor.first.value,
source:"CRAIG",
category_group: "VVVV",
category: "VAUT",
'location.country' => "USA",
retvals: "location,external_url,heading,body,timestamp,price,images,annotations"
}
# Prepare API request
uri = URI.parse(polling_url)
uri.query = URI.encode_www_form(params)
# Submit request
result = JSON.parse(open(uri).read)
# Display results to screen
#puts result["postings"].first["annotations"]["year"]
Anchor.first.update(value: result["anchor"])
puts Anchor.first.value
break if result["postings"].empty?
# #store results in Database
result["postings"].each do |posting|
#ADD HARD FILTER (IN PROGRESS....)
if posting["annotations"]["make"] == "Jeep"
#create new post
#post= Post.new
#post.heading = posting["heading"]
#post.body = posting["body"]
#post.price = posting["price"]
#post.neighborhood = posting["location"]["locality"]
#post.external_url = posting["external_url"]
#post.timestamp = posting["timestamp"]
#post.year = posting ["annotations"]["year"] if posting ["annotations"]["year"].present?
#post.make = posting ["annotations"]["make"] if posting ["annotations"]["make"].present?
#post.model = posting ["annotations"]["model"] if posting ["annotations"]["model"].present?
#post.title_status = posting ["annotations"]["title_status"] if posting ["annotations"]["title_status"].present?
#post.transmission = posting ["annotations"]["transmission"] if posting ["annotations"]["transmission"].present?
#post.mileage = posting ["annotations"]["mileage"] if posting ["annotations"]["mileage"].present?
#post.source_account = posting ["annotations"]["source_account"] if posting ["annotations"]["source_account"].present?
#post.phone = posting ["annotations"]["phone"] if posting ["annotations"]["phone"].present?
#post.lat = posting["location"]["lat"]
#post.lng = posting["location"]["long"]
#post.zipcode = posting["location"]["zipcode"]
#Save Post
#post.save
# Loop over images and save to Image database
posting["images"].each do |image|
#image = Image.new
#image.url = image["full"]
#image.post_id = #post.id
#image.save
end
end
end
end
end
desc "Destroy All Posting Data"
task destroy_all_posts: :environment do
Post.destroy_all
end
desc "Save neighborhood codes in a reference table"
task scrape_neighborhoods: :environment do
require 'open-uri'
require 'json'
# Set API token and URL
auth_token = "b077632d17da8857e2fa92c053115e43"
location_url = "http://reference.3taps.com/locations"
# Specify request parameters
params = {
auth_token: auth_token,
level: "locality",
country: "USA"
}
# Prepare API request
uri = URI.parse(location_url)
uri.query = URI.encode_www_form(params)
# Submit request
result = JSON.parse(open(uri).read)
# Display results to screen
# puts JSON.pretty_generate result
# Store results in database
result["locations"].each do |location|
#location = Location.new
#location.code = location["code"]
#location.name = location["short_name"]
#location.save
end
end
desc "Discard old data"
task discard_old_data: :environment do
Post.all.each do |post|
if post.created_at < 72.hours.ago
post.destoy
end
end
end
end

Answer 1

Your error message is saying it all:
NoMethodError: undefined method `value' for nil:NilClass
You are trying to call value on nil at some point. And, this is probably happening here:
# Specify request parameters
params = {
auth_token: auth_token,
anchor: Anchor.first.value, # this is the line that's creating problem
source:"CRAIG",
category_group: "VVVV",
category: "VAUT",
'location.country' => "USA",
retvals: "location,external_url,heading,body,timestamp,price,images,annotations"
}
When you call this: anchor: Anchor.first.value for the very first time, your Anchor.first is nil and so you are trying to call: nil.value and that's where your rake task fails with the specified error message.
Make sure you have populated the database table (anchors) so that when you call Anchor.first, you don't get nil.
Another approach to avoid this issue would be to use try:
anchor: Anchor.first.try(:value)
That way, your rake task won't fail even if Anchor.first returns nil.