Why does it output one document, when it used to output multiple? - ruby

Question

This used to output a document for each person on the list. But since I added the code to determine the most popular date & time for a list of given dates, it now only outputs one document for the first person in the list.
def save_thank_you_letters(id,form_letter)
Dir.mkdir("output") unless Dir.exists?("output")
filename = "output/thanks_#{id}.html"
File.open(filename,'w') do |file|
file.puts form_letter
end
end
puts "EventManager initialized."
contents = CSV.open 'event_attendees.csv', headers: true, header_converters: :symbol
template_letter = File.read "form_letter.erb"
erb_template = ERB.new template_letter
contents.each do |row|
id = row[0]
name = row[:first_name]
zipcode = clean_zipcode(row[:zipcode])
phone = clean_phonenumber(row[:homephone])
legislators = legislators_by_zipcode(zipcode)
form_letter = erb_template.result(binding)
save_thank_you_letters(id,form_letter)
# IT WORKS OK UNTIL I ADD THIS PART...
times = contents.map { |row| row[:regdate] }
target_times = Hash[times.group_by do |t|
DateTime.strptime(t, '%m/%d/%y %H:%M').hour
end.map do |k,v|
[k, v.count]
end.sort_by do |k,v|
v
end.reverse]
target_days = Hash[times.group_by do |t|
DateTime.strptime(t, '%m/%d/%y %H:%M').wday
end.map do |k,v|
[Date::ABBR_DAYNAMES[k], v.count]
end.sort_by do |k,v|
v
end.reverse]
puts target_times
puts target_days
end
I think it is something to do with the way that I am processing the data from the date/time data. If I remove this, I get an html document for each person on the list. But if I include it, I get the date & time info that I am looking for — but it only generates a document for the first person in the list.
Can someone please explain why what I am doing does not work? I would like it to print the times and the days of the week, but ALSO generate an html document for each person on the list.
Thanks!

Answer 1

When you read CSV file, you read it line by line moving internal pointer. Once you reached the end of file, this pointer stays there so every time you try to fetch new row you'll get nil unless you rewind the file. So, your code started iteration on this line:
contents.each do |row|
This fetched the first row and moved the cursor to the next line. However inside the loop you did contents.map {...} which read the whole csv file and left the curses at the end of the file.
So to fix it you need to move the statistic bits outside the loop (before or after) and rewind the file (reset the cursor) before second iteration:
contents.each do |row|
id = row[0]
name = row[:first_name]
zipcode = clean_zipcode(row[:zipcode])
phone = clean_phonenumber(row[:homephone])
legislators = legislators_by_zipcode(zipcode)
form_letter = erb_template.result(binding)
save_thank_you_letters(id,form_letter)
end
contents.rewind
times = contents.map { |row| row[:regdate] }
target_times = Hash[times.group_by do |t|
DateTime.strptime(t, '%m/%d/%y %H:%M').hour
end.map do |k,v|
[k, v.count]
end.sort_by do |k,v|
v
end.reverse]
target_days = Hash[times.group_by do |t|
DateTime.strptime(t, '%m/%d/%y %H:%M').wday
end.map do |k,v|
[Date::ABBR_DAYNAMES[k], v.count]
end.sort_by do |k,v|
v
end.reverse]
puts target_times
puts target_days