Ruby <NoMethodError> - ruby

Question

I'm using the following script to download FFFFound entire directory images but im having an issue, after the first batch of files Im getting this error message:
ffffound_mirror_db.rb:45in 'block in populate_db': undefined method 'inner_html' for nil:NilClass <NoMethodError>
from ffffound_mirror_db.rb:39:in 'each'
from ffffound_mirror_db.rb:39:in 'populate_db'
from ffffound_mirror_db.rb:190:in <main>
I'm trying to download all the 99 pages of a directory so the offset has to increase 25 every batch, eg: 0, 25, 50, 75, 100
#!/usr/bin/ruby
require 'rubygems'
require 'etc'
require 'hpricot'
require 'json'
require 'open-uri'
require 'sqlite3'
require 'time'
require 'date'
require 'fileutils'
def populate_db(db, user, type)
domain = "http://ffffound.com/"
offset = 0
images_sql = <<EOS
INSERT OR REPLACE INTO
images (id, url, src, title, orig_url, orig_src, count, date, related)
values (:id, :ffffound_url, :ffffound_img, :title, :orig_url, :orig_img, :count, :date, :rel)
EOS
images_ins = db.prepare(images_sql)
# related_ins = db.prepare( "insert into related values (?, ?, ?)" )
img = []
while
if user == "all" # wow, this is naughty
doc = Hpricot(open("#{ domain }/?offset=#{ offset }&"))
else
doc = Hpricot(open("#{ domain }/home/#{ user }/#{ type }/?offset=#{ offset }&"))
end
images = (doc/"blockquote.asset")
puts "Got #{ images.size.to_s } images at offset #{ offset.to_s }"
break if (images.size == 0)
images.each do |image|
# can I make this block into a method somehow?
info = {}
# image title
title_elem = (image/"div.title")
info[:title] = title_elem.at("a").inner_html
# original source image
src_elem = (image/"div.title")
info[:orig_url] = src_elem.at("a")["href"]
# from description, break out img url, date posted (relative!), count
desc_elem = (image/"div.description")
desc = desc_elem.inner_html
info[:orig_img] = desc.gsub(/<br ?\/?>.*/, "")
datestr = desc.gsub(/.*<br ?\/?>/, "")
datestr = datestr.gsub(/<a h.*/, "")
datestr = datestr+" +0900" # ffffound uses Japanese time, UTC +0900
begin
dt = Time.parse(datestr)
rescue
end
info[:date] = dt.to_i
count = desc_elem.at("a").inner_text
count = count.gsub(/[\D]/, "")
info[:count] = count
# ffffound image URL and page URL, and ffffound ID (could generate
# URL from ID but would lose ?c form; src would lose _m)
image_block = (image/"table td")
ffffound_url = image_block.at("a")['href']
ffffound_img = image_block.at("img")['src']
id = ffffound_img
id = ffffound_img.split('/')[6]
id = id.gsub(/_.*/, "")
info[:id] = id
info[:ffffound_url] = ffffound_url
info[:ffffound_img] = ffffound_img
download_file(ffffound_img, id)
# might as well get related asset IDs
rel = Array.new
relateds = (image/"div.related_to_item_xs")
relateds.each do |related|
path = related.at("a")['href']
id = path[ path.index(/\//, 2)+1 .. -1 ]
rel.push(id)
# TODO normalised table for related IDs
end
info[:rel] = rel.join(",")
img.unshift(info)
# put in db
images_ins.execute(info)
end
break if (images.size < 25) # more efficient than doing another fetch
offset = offset + 25
end
puts "Got #{ img.size } images"
end
def create_db(db)
images = <<EOC
CREATE TABLE IF NOT EXISTS
images (id TEXT PRIMARY KEY,
url TEXT,
src TEXT,
title TEXT,
orig_url TEXT,
orig_src TEXT,
date INTEGER,
count INTEGER,
related TEXT,
posted BOOL);
EOC
related = <<EOC
CREATE TABLE IF NOT EXISTS
related (id INTEGER PRIMARY KEY,
source INTEGER
related INTEGER);
EOC
tumblr = <<EOC
CREATE TABLE tumblr (id INTEGER PRIMARY KEY,
ffffound_id TEXT,
tumblr_id INTEGER,
create_status INTEGER,
edit_status INTEGER);
EOC
db.execute(images)
db.execute(related)
return true
end
def download_file(url, id)
# TODO file type awareness
# does it exist?
if not File.exist?('images/'+id+'.jpg')
writeOut = open("images/"+id+'.jpg', 'wb')
writeOut.write(open(url).read)
writeOut.close
puts ' downloaded ' + id
end
end
def create_paths()
['images', 'db'].each do |path|
if not File.exist?(path)
FileUtils.mkdir(path)
end
end
end
# this needs work (is there a more idiomatic way to do this?)
user = ARGV[0]
type = ARGV[1] || 'found'
if not user
puts "A ffffound username must be supplied"
exit
else
if user == "--all"
puts "Invoked for all posts"
user = "all"
end
puts "Invoked for posts by #{user} of type #{type}"
end
create_paths()
path = 'db/ffffound-'+user+'.db' # ick
db = SQLite3::Database.new(path)
create_db(db)
populate_db(db, user, type)
exit
# puts img.to_json
# DONE puts img.to_database_table(s)

Answer 1

In these 2 parts:
title_elem = (image/"div.title")
info[:title] = title_elem.at("a").inner_html
desc_elem = (image/"div.description")
desc = desc_elem.inner_html
You don't check if elem exists, but calling inner_html right after. So, basically, if desc_elem is nil, you call nil.inner_html which raises exception, because there is no such method for nil.
To fix this, replace corresponding lines with(for Ruby without Rails)
title_elem = (image/"div.title")
info[:title] = title_elem.at("a").inner_html unless title_elem.at("a").nil?
desc_elem = (image/"div.description")
desc = desc_elem.inner_html unless desc_elem.nil?
In Rails there is a .try method, which prevents such exception raising, so
title_elem = (image/"div.title")
info[:title] = title_elem.at("a").try(:inner_html)
desc_elem = (image/"div.description")
desc = desc_elem.try(:inner_html)
is a solution if you are using Rails.