I'm new to programming in Ruby.
How do I make the output show Revenue and Profit or Loss?
How can I refactor the following code to look neater? I know it's wrong but I have no idea how to take my if profit out of the initialize method.
class Theater
attr_accessor :ticket_price, :number_of_attendees, :revenue, :cost
def initialize
puts "What is your selling price of the ticket?"
#ticket_price = gets.chomp.to_i
puts "How many audience are there?"
#number_of_attendees = gets.chomp.to_i
#revenue = (#number_of_attendees * #ticket_price)
#cost = (#number_of_attendees * 3) + 180
#profit = (#revenue - #cost)
if #profit > 0
puts "Profit made: $#{#profit}"
else
puts "Loss incurred: $#{#profit.abs}"
end
end
end
theater = Theater.new
# theater.profit
# puts "Revenue for the theater is RM#{theater.revenue}."
# I hope to put my Profit/Loss here
#
# puts theater.revenue
Thanks guys.
Do not initialize the object with input from the user, make your object accept the needed values. Make a method to read the needed input and return you new Theater. Last of all put the if in separate method like #report_profit.
Remember constructors are for setting up the initial state of the object, making sure it is in a valid state. The constructor should not have side effects(in your case system input/output). This is something to be aware for all programming languages, not just ruby.
Try this:
class Theatre
COST = { running: 3, fixed: 180 }
attr_accessor :number_of_audience, :ticket_price
def revenue
#number_of_audience * #ticket_price
end
def total_cost
COST[:fixed] + (#number_of_audience * COST[:running])
end
def net
revenue - total_cost
end
def profit?
net > 0
end
end
class TheatreCLI
def initialize
#theatre = Theatre.new
end
def seek_number_of_attendes
print 'Number of audience: '
#theatre.number_of_audience = gets.chomp.to_i
end
def seek_ticket_price
print 'Ticket price: '
#theatre.ticket_price = gets.chomp.to_i
end
def print_revenue
puts "Revenue for the theatre is RM #{#theatre.revenue}."
end
def print_profit
message_prefix = #theatre.profit? ? 'Profit made' : 'Loss incurred'
puts "#{message_prefix} #{#theatre.net.abs}."
end
def self.run
TheatreCLI.new.instance_eval do
seek_ticket_price
seek_number_of_attendes
print_revenue
print_profit
end
end
end
TheatreCLI.run
Notes:
Never use your constructor (initialize method) for anything other than initial setup.
Try to keep all methods under 5 lines.
Always try to keep each class handle a single responsibility; for instance, printing and formatting output is not something the Theatre class needs to care.
Try extracting all hard coded values; eg see the COST hash.
Use apt variables consistent to the domain. Eg: net instead of profit makes the intent clear.
Related
I recently wrote a program to return a bunch of stocks from the stock market that are unhealthy. The basic algorithm is this:
Look up all the quotes of every stock in an exchange (either NYSE or NASDAQ)
Find the ones that are less than 5 dollars from step 1
Find the ones from step 2 that are down 3 days and have large volume (expensive because I have to make a request for each stock, which is like ~700 currently for nasdaq).
Scan the news for the ones returned by step 3.
I had this all in one file:
Original implementation (https://github.com/EdmundMai/minion/blob/aa14bc3234a4953e7273ec502276c6f0073b459d/lib/minion.rb):
require 'bundler/setup'
require "minion/version"
require "yahoo-finance"
require "business_time"
require 'nokogiri'
require 'open-uri'
module Minion
class << self
def query(exchange)
client = YahooFinance::Client.new
all_companies = CSV.read("#{exchange}.csv")
small_caps = []
ticker_symbols = all_companies.map { |row| row[0] }
ticker_symbols.each_slice(200) do |batch|
data = client.quotes(batch, [:symbol, :last_trade_price, :average_daily_volume])
small_caps << data.select { |stock| stock.last_trade_price.to_f < 5.0 }
end
attractive = []
small_caps.flatten!.each_with_index do |small_cap, index|
begin
data = client.historical_quotes(small_cap.symbol, { start_date: 2.business_days.ago, end_date: Time.now })
closing_prices = data.map(&:close).map(&:to_f)
volumes = data.map(&:volume).map(&:to_i)
negative_3_days_in_a_row = closing_prices == closing_prices.sort
larger_than_average_volume = volumes.reduce(:+) / volumes.count > small_cap.average_daily_volume.to_i
if negative_3_days_in_a_row && larger_than_average_volume
attractive << small_cap.symbol
puts "Qualified: #{small_cap.symbol}, finished with #{index} out of #{small_caps.count}"
else
puts "Not qualified: #{small_cap.symbol}, finished with #{index} out of #{small_caps.count}"
end
rescue => e
puts e.inspect
end
end
final_results = []
attractive.each do |symbol|
rss_feed = Nokogiri::HTML(open("http://feeds.finance.yahoo.com/rss/2.0/headline?s=#{symbol}®ion=US&lang=en-US"))
html_body = rss_feed.css('body')[0].text
diluting = false
['warrant', 'cashless exercise'].each do |keyword|
diluting = true if html_body.match(/#{keyword}/i)
end
final_results << symbol if diluting
end
final_results
end
end
end
This was really fast and would finish processing like ~700 stocks in a minute or less.
Then, I tried refactoring and splitting up the algorithm into different classes and files without changing the algorithm at all. I decided on using the decorator pattern since it seems to fit. However when I run the program now, it makes each request really slowly (15+ min). I know this because my puts statements get printed out really slowly.
New and slower implementation (https://github.com/EdmundMai/minion/blob/master/lib/minion.rb)
require 'bundler/setup'
require "minion/version"
require "yahoo-finance"
require "minion/dilution_finder"
require "minion/negative_finder"
require "minion/small_cap_finder"
require "minion/market_fetcher"
module Minion
class << self
def query(exchange)
all_companies = CSV.read("#{exchange}.csv")
all_tickers = all_companies.map { |row| row[0] }
short_finder = DilutionFinder.new(NegativeFinder.new(SmallCapFinder.new(MarketFetcher.new(all_tickers))))
short_finder.results
end
end
end
The part it's lagging at according to my puts:
require "yahoo-finance"
require "business_time"
require_relative "stock_finder"
class NegativeFinder < StockFinder
def results
client = YahooFinance::Client.new
results = []
finder.results.each_with_index do |stock, index|
begin
data = client.historical_quotes(stock.symbol, { start_date: 2.business_days.ago, end_date: Time.now })
closing_prices = data.map(&:close).map(&:to_f)
volumes = data.map(&:volume).map(&:to_i)
negative_3_days_in_a_row = closing_prices == closing_prices.sort
larger_than_average_volume = volumes.reduce(:+) / volumes.count > stock.average_daily_volume.to_i
if negative_3_days_in_a_row && larger_than_average_volume
results << stock
puts "Qualified: #{stock.symbol}, finished with #{index} out of #{finder.results.count}"
else
puts "Not qualified: #{stock.symbol}, finished with #{index} out of #{finder.results.count}"
end
rescue => e
puts e.inspect
end
end
results
end
end
It's lagging on step 3 (making one request for each stock). Not sure what's going on so any advice would be appreciated. If you want to clone the program and run it, just comment in the last line in lib/minion.rb and type ruby lib/minion.rb
After debugging it I figured it out. It was because I was calling finder.results (results being the decorated method) inside of the loop as shown below:
require 'bundler/setup'
require "minion/version"
require "yahoo-finance"
require "minion/dilution_finder"
require "minion/negative_finder"
require "minion/small_cap_finder"
require "minion/market_fetcher"
module Minion
class << self
def query(exchange)
all_companies = CSV.read("#{exchange}.csv")
all_tickers = all_companies.map { |row| row[0] }
short_finder = DilutionFinder.new(NegativeFinder.new(SmallCapFinder.new(MarketFetcher.new(all_tickers))))
short_finder.results
end
end
end
The part it's lagging at according to my puts:
require "yahoo-finance"
require "business_time"
require_relative "stock_finder"
class NegativeFinder < StockFinder
def results
client = YahooFinance::Client.new
results = []
finder.results.each_with_index do |stock, index|
begin
data = client.historical_quotes(stock.symbol, { start_date: 2.business_days.ago, end_date: Time.now })
closing_prices = data.map(&:close).map(&:to_f)
volumes = data.map(&:volume).map(&:to_i)
negative_3_days_in_a_row = closing_prices == closing_prices.sort
larger_than_average_volume = volumes.reduce(:+) / volumes.count > stock.average_daily_volume.to_i
if negative_3_days_in_a_row && larger_than_average_volume
results << stock
// HERE!!!!!!!!!!!!!!!!!!!!!!!!!
puts "Qualified: #{stock.symbol}, finished with #{index} out of #{finder.results.count}" <------------------------------------
else
// AND HERE!!!!!!!!!!!!!!!!!!!!!!!!!
puts "Not qualified: #{stock.symbol}, finished with #{index} out of #{finder.results.count}" <-----------------------------------------------------------
end
rescue => e
puts e.inspect
end
end
results
end
end
This caused a cascade of requests every time I iterated through the loop in NegativeFinder. Removing that call fixed it. Lesson: When using the decorator pattern, either only call the decorated method once, especially when you're doing something expensive in each call. Either that or hold the returned variable in an instance variable so you don't have to calculate it each time.
Also as a side note, I've decided not to go with the decorator pattern because I don't think it applies well here. Something like SmallCapFinder.new(SmallCapFinder.new(MarketFetcher.new(all_tickers))) doesn't add functionality at all (the primary function of using the decorator pattern), so chaining decorators doesn't do anything. Therefore, I'm just going to make them methods instead of adding unnecessary complexity.
There are some thing missing in the code you gave us (Base class StockFinder, MarketFetcher). But I think you are now instantate more than one YahooFinance::Client. Input/Output to other systems is very often the cause for speed problems.
I suggest that you first encapsulate the finance client and access to financial data. This makes it easier when you want to switch your financial data provider, or add another one. Instead of the decorator pattern, I would just use plain old methods for finding small caps, finding negative, etc.
I have this sample code, which is essentially just a few basic classes for working with mdii files
class Array
def to_midi(file, note_length='eighth')
midi_max = 108.0
midi_min = 21.0
low, high = min, max
song = MIDI::Sequence.new
# Create a new track to hold the melody, running at 120 beats per minute.
song.tracks << (melody = MIDI::Track.new(song))
melody.events << MIDI::Tempo.new(MIDI::Tempo.bpm_to_mpq(120))
# Tell channel zero to use the "piano" sound.
melody.events << MIDI::ProgramChange.new(0, 0)
# Create a series of note events that play on channel zero.
each do |number|
midi_note = (midi_min + ((number-midi_min) * (midi_max-low)/high)).to_i
melody.events << MIDI::NoteOnEvent.new(0, midi_note, 127, 0)
melody.events << MIDI::NoteOffEvent.new(0, midi_note, 127,
song.note_to_delta(note_length))
end
open(file, 'w') { |f| song.write(f) }
end
end
class TimedTrack < MIDI::Track
MIDDLE_C = 60
##channel_counter=0
def initialize(number, song)
super(number)
#sequence = song
#time = 0
#channel = ##channel_counter
##channel_counter += 1
end
# Tell this track's channel to use the given instrument, and
# also set the track's instrument display name.
def instrument=(instrument)
#events << MIDI::ProgramChange.new(#channel, instrument)
super(MIDI::GM_PATCH_NAMES[instrument])
end
# Add one or more notes to sound simultaneously. Increments the per-track
# timer so that subsequent notes will sound after this one finishes.
def add_notes(offsets, velocity=127, duration='quarter')
offsets = [offsets] unless offsets.respond_to? :each
offsets.each do |offset|
event(MIDI::NoteOnEvent.new(#channel, MIDDLE_C + offset, velocity))
end
#time += #sequence.note_to_delta(duration)
offsets.each do |offset|
event(MIDI::NoteOffEvent.new(#channel, MIDDLE_C + offset, velocity))
end
recalc_delta_from_times
end
# Uses add_notes to sound a chord (a major triad in root position), using the
# given note as the low note. Like add_notes, increments the per-track timer.
def add_major_triad(low_note, velocity=127, duration='quarter')
add_notes([0, 4, 7].collect { |x| x + low_note }, velocity, duration)
end
private
def event(event)
#events << event
event.time_from_start = #time
end
end
most of it makes perfect sense to me except for the lines that use the << operator, from all of my research the only reason to use a << is when your defining a class that will be a singleton. So in what way specifically is the << being used in this code?
From https://github.com/jimm/midilib:
MIDI::Track is a track that contains an array of events.
So with << you're adding events to your track. It is the same as
melody.events.push(MIDI::NoteOnEvent.new(0, midi_note, 127, 0))
<< could also be used for bit shifting operations
http://calleerlandsson.com/2014/02/06/rubys-bitwise-operators/
<< operator may be used either for bitwise operations (quite unlikely here) or may be overloaded inside the class to match some behavior. In this case there is (probably) an Array object and thus the event is pushed into the #events array via this operator. More info about this use case can be found here.
Take notice, that in future you can bump into other situations where this operator is used and not everytime it will mean same thing - it depends on library creator. The other use case that comes into mind right now can be ActiveRecord Relationships, as has_many where also you can use this operator to immediately push an object to relationship and save. More info about this one can be found in api docs here. Quick sample:
class User < ActiveRecord::Base
has_many :posts
end
class Post < ActiveRecord::Base
belongs_to :user
end
And then somewhere in code you can use:
#post = Post.find(10)
#user = User.find(1)
#user.posts << #post
# automatically save the #post object with updated foreign key
Forgive me if my question isn't completely clear. I have been awake for way too long and I'm feeling a little brain dead.
I'm doing a Ruby exercise and I can't figure out why my rspec test isn't passing for something I thought would work.
require 'date'
class Product
attr_accessor :photo_src, :promotion, :initial_date
attr_reader :default_photo, :default_price, :current_price
def initialize(name, photo, price)
#name = name
#default_photo = photo
#photo_src = photo
#default_price = price
#current_price = price
#initial_date = Date.today.yday
#promotion = false
end
def price_change(sale_price)
calculator = RedPencilCalculator.new(self)
if promotion
if sale_price > #current_price
calculator.end_promotion!
elsif sale_price < (#default_price - (#default_price * 0.3))
calculator.end_promotion!
end
else
calculator.start_promotion!
end
#current_price = sale_price
end
end
class RedPencilCalculator
attr_accessor :promotion_start, :product
def initialize(product)
#product = product
end
def start_promotion!
if start_promotion?
product.promotion = true
product.photo_src = "redX.png"
#promotion_start = Date.today.yday
end
end
#would need to run daily
def end_promotion?
promotion_duration
if #duration == 30 || #duration == 335
end_promotion!
end
end
def end_promotion!
product.promotion = false
product.photo_src = product.default_photo
product.initial_date = Date.today.yday
end
private
def calculate_range
#min_discount = product.default_price - (product.default_price * 0.05)
#max_discount = product.default_price - (product.default_price * 0.3)
end
def start_promotion?
calculate_range
#max_discount <= product.current_price && product.current_price <= #min_discount && Date.today.yday - product.initial_date >= 30
end
def promotion_duration
current_date = Date.today.yday
#duration = current_date - #promotion_start
end
end
Rspec
This doesn't work:
describe Product do
let(:shoes) { Product.new("shoes", "item.png", 100) }
it 'should change the photo_src and promotion attribute if applicable' do
allow(shoes).to receive(:initial_date) { 100 }
shoes.price_change(75)
expect(shoes.promotion).to eq(true)
expect(shoes.photo_src).to eq("redX.png")
end
end
This does:
describe Product do
let(:shoes) { Product.new("shoes", "item.png", 100) }
let(:calculator) { RedPencilCalculator.new(shoes) }
it 'should change the photo_src and promotion attribute if applicable' do
allow(shoes).to receive(:initial_date) { 100 }
shoes.price_change(75)
calculator.start_promotion!
expect(shoes.promotion).to eq(true)
expect(shoes.photo_src).to eq("redX.png")
end
end
So it seems to me that the start_promotion! method call in the price_change method just isn't working.
I don't have a specific answer to your bug but some suggestions on how to pinpoint the problem.
You're testing too much in one unit test. There's so much that can go wrong it's hard (as you've found) to track down where the bug lies. Even if you work it out now, when something changes down the track (as it inevitably will) it will be at least as difficult as it is now to debug.
Simplify the initializer. It should only set #name, #photo, #price. The other instance variables should be methods (write tests unless they're private).
You suspect RedPencilCalculator#start_promotion! has a bug. Write a test to eliminate that possibility.
With more tests in place, the bug will eventually be cornered and crushed!
Lastly - this is easier said than done - but try writing tests first. It is hard but gets easier and even enjoyable!
ok, I put a puts inside of start_promotion? like this:
p "got past calc range: #{#max_discount.inspect} and #{#min_discount.inspect} and #{product.current_price}"
and got:
"got past calc range: 70.0 and 95.0 and 100"
given that the following line checks that current-price is less than the min-discount...
that's the line you've gotta check/fix to make things work
I have written some code out of the Ruby Pickaxe book and I am trying to get it to work.
(around page 62 of "Programming Ruby The Pragmatic Programmer's Guide")
**Edit: More info on the book: (C) 2009, for Ruby 1.9
Given this error message, I am not quite sure how to identify what is going wrong. I appreciate any help in understanding what is going wrong here.
How does one know what to identify and solve?
I am wondering if Ruby's CSV functionality is really just this easy-- no gem/bundle install to run?
I would really like to be able to run my test_code.rb file, but I am unable to figure out this error.
Thank you for your time,
Patrick
Note: all of these files are in the same directory.
IRB command, followed by the error message it generates:
2.1.1 :005 > load "test_code.rb"
LoadError: cannot load such file -- csv-reader
from /Users/patrickmeaney/.rvm/rubies/ruby-2.1.1/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/patrickmeaney/.rvm/rubies/ruby-2.1.1/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from test_code.rb:3:in `<top (required)>'
from (irb):5:in `load'
from (irb):5
from /Users/patrickmeaney/.rvm/rubies/ruby-2.1.1/bin/irb:11:in `<main>'
I don't know how relevant this is, based on the error message, but thought I'd include it.
kernel_require.rb line 55:
if Gem::Specification.unresolved_deps.empty? then
begin
RUBYGEMS_ACTIVATION_MONITOR.exit
return gem_original_require(path)
ensure
RUBYGEMS_ACTIVATION_MONITOR.enter
end
end
line 9-11 of irb:
require "irb"
IRB.start(__FILE__)
First file of program: csv-reader.rb
require 'csv'
require 'book-in-stock'
class CsvReader
def initialize
#books_in_stock = []
end
def read_in_csv_data(csv_file_name)
CSV.foreach(csv_file_name, headers: true) do |row|
#books_in_stock << BookInStock.new(row["ISBN"], row["Amount"])
end
end
def total_value_in_stock
sum = 0.0
#books_in_stock.each {|book| sum += book.price}
end
def number_of_each_isbn
end
end
Second file: book-in-stock.rb
class BookInStock
attr_reader :isbn
attr_accessor :price
def initialize(isbn, price)
#isbn = isbn
#price = Float(price)
end
def price_in_cents
Integer(price*100 + 0.5)
end
def price_in_cents=(cents)
#price = cents / 100.0
end
end
Third file: stock-stats.rb
require 'csv-reader'
reader = CsvReader.new
ARGV.each do |csv_file_name|
STDERR.puts "Processing #{csv_file_name}"
reader.read_in_csv_data(csv_file_name)
end
puts "Total value = #{reader.total_value_in_stock}"
Fourth file: test_code.rb
# this is the test code file
require 'csv-reader'
require 'book-in-stock'
require 'stock-stats'
# code to call
reader = CsvReader.new
reader.read_in_csv_data("file1.csv")
reader.read_in_csv_data("file2.csv")
puts "Total value in stock = #{reader.total_value_in_stock}"
# code to call
book = BookInStock.new("isbn1", 33.80)
puts "Price = #{book.price}"
puts "Price in cents = #{book.price_in_cents}"
book.price_in_cents = 1234
puts "Price = #{book.price}"
puts "Price in cents = #{book.price_in_cents}"
CSV files:
file1.csv
ISBN, Amount
isbn1, 49.00
isbn2, 24.54
isbn3, 33.23
isbn4, 15.55
file2.csv
ISBN, Amount
isbn5-file2, 39.98
isbn6-file2, 14.84
isbn7-file2, 43.63
isbn8-file2, 25.55
Edit
After Frederick Cheung's suggestion to change require to require_relative (for all but the 1st line of csv-reader.rb), the script is running, but a method is not working (see below)
(I did receive an error about this line:
#price = Float(price)
and changed it to #price = price.to_f and it runs just fine. )
3 Questions:
-> I changed the header of my csv files to "ISBN, Amount". Previously Amount was amount (not capitalized). Does this matter (i.e. the capitalizing of the header)?
-> While we're on the subject, what is the "row" keyword doing in the following #read_in_csv_data method?
-> Now that my code runs it appears that the output for "Total value in stock" is not summing up all of the prices in the csv file. Could a Rubyist please help me understand why this is happening?
The method
def read_in_csv_data(csv_file_name)
CSV.foreach(csv_file_name, headers: true) do |row|
#books_in_stock << BookInStock.new(row["ISBN"], row["Amount"])
end
end
and call seem fine to me...
reader = CsvReader.new
reader.read_in_csv_data("file1.csv")
reader.read_in_csv_data("file2.csv")
Here is the current output from terminal:
Total value = []
Price = 33.8
Price in cents = 3380
Price = 12.34
Price in cents = 1234
Total value in stock = [#<BookInStock:0xb8168a60 #isbn="isbn1", #price=0.0>, #<BookInStock:0xb8168740 #isbn="isbn2", #price=0.0>, #<BookInStock:0xb8168358 #isbn="isbn3", #price=0.0>, #<BookInStock:0xb81546f0 #isbn="isbn4", #price=0.0>, #<BookInStock:0xb8156a18 #isbn="isbn5-file2", #price=0.0>, #<BookInStock:0xb8156784 #isbn="isbn6-file2", #price=0.0>, #<BookInStock:0xb81564a0 #isbn="isbn7-file2", #price=0.0>, #<BookInStock:0xb8156248 #isbn="isbn8-file2", #price=0.0>]
Thanks again.
Edit: Big thanks to 7Stud for a very thorough followup answer on every question I had. You have been exceptionally helpful. I have learned several important things thanks to your post.
Edit:
Still not able to get the code to run.
I am not sure how to add to / edit the $LOAD_PATH, so I tried putting all of the files into this directory:
directory: ~MY_RUBY_HOME/lib/ruby/site_ruby/2.1.0/csv-reader
(i.e. /Users/patrickmeaney/.rvm/rubies/ruby-2.1.1/lib/ruby/site_ruby/2.1.0/csv-reader)
However, I still receive the same error message:
✘ ~MY_RUBY_HOME/lib/ruby/site_ruby/2.1.0/csv-reader ruby test_code.rb file1.csv file2.csv
/Users/patrickmeaney/.rvm/rubies/ruby-2.1.1/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- ./csv_reader (LoadError)
from /Users/patrickmeaney/.rvm/rubies/ruby-2.1.1/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from test_code.rb:1:in `<main>'
I have written some code out of the Ruby Pickaxe book
Yeah, but there are many Ruby Pickaxe books.
IRB command, followed by the error message it generates:
NEVER run anything in IRB. Never use IRB for ANYTHING. Instead put your code in a file, and then run the file, e.g:
$ ruby my_prog.rb
LoadError: cannot load such file -- csv-reader
If the files you want to require are not located in the directories ruby searches automatically(to see those directories execute the line `p $LOAD_PATH'), then you can specify the absolute or relative path to the file you want to require in the require statement:
require './book_in_stock'
I did receive an error about this line: #price = Float(price) and
changed it to #price = price.to_f and it runs just fine.
x = 'hello'
p x.to_f
p Float(x)
--output:--
0.0
1.rb:3:in `Float': invalid value for Float(): "hello" (ArgumentError)
from 1.rb:3:in `<main>
The difference between Float() and to_f() is that Float will raise an exception when it is unable to convert the String to a Float, while to_f() will return 0 when it cannot convert the String to a Float. Unless you know what you are doing, it's probably best to use Float(), so that you are alerted to the fact that your data has an error in it.
While we're on the subject, what is the "row" keyword doing in the
following #read_in_csv_data method?
When you loop through the rows of your file(e.g. CSV.foreach), csv converts one row of your file into a thing called a "CSV::Row", and then assigns the "CSV::ROW" object to the loop variable, which you have named "row":
CSV.foreach(csv_file_name, headers: true) do |row|
^
|
So "row" is a variable that refers to a "CSV::Row". A "CSV::Row" acts like a hash, enabling you to write things like row['ISBN'] to retrieve the value in that column.
Spaces are significant in csv files. If your header row is ISBN, Amount, then the column names are "ISBN" and " Amount" (see the leading space?). That means there is no value for
row['Amount']
i.e. it will return nil, but there is a value for
row[' Amount']
^
|
Now that my code runs it appears that the output for "Total value in
stock" is not summing up all of the prices in the csv file. Could a
Rubyist please help me understand why this is happening?
1) A def returns the value of the last statement that was executed in the def.
2) Array#each() returns the array.
Here is your def:
def total_value_in_stock
sum = 0.0
#books_in_stock.each {|book| sum += book.price}
end
That def returns the #books_in_stock array. You need to return the sum:
def total_value_in_stock
sum = 0.0
#books_in_stock.each {|book| sum += book.price}
sum
end
If you want to get tricky, you can have csv automatically convert any data in your file that looks like a number to a number:
CSV.foreach(
csv_file_name,
headers: true,
:converters => :numeric
) do |row| ...
...then your BookInStock class would look like this:
class BookInStock
attr_reader :isbn
attr_accessor :price
def initialize(isbn, price)
#isbn = isbn
#price = price #Float(price)
end
Here are all your files amended so they will run correctly:
csv_reader.rb:
require 'csv'
require './book_in_stock'
class CsvReader
def initialize
#books_in_stock = []
end
def read_in_csv_data(csv_file_name)
CSV.foreach(csv_file_name, headers: true) do |row|
#books_in_stock << BookInStock.new(row["ISBN"], row["Amount"])
end
end
def total_value_in_stock
sum = 0.0
#books_in_stock.each {|book| sum += book.price}
sum
end
def number_of_each_isbn
end
end
stock_stats.rb:
require './csv_reader'
reader = CsvReader.new
ARGV.each do |csv_file_name|
STDERR.puts "Processing #{csv_file_name}"
reader.read_in_csv_data(csv_file_name)
end
puts "Total value = #{reader.total_value_in_stock}"
test_code.rb:
require './csv_reader'
require './book_in_stock'
require './stock_stats'
reader = CsvReader.new
reader.read_in_csv_data("file1.csv")
reader.read_in_csv_data("file2.csv")
puts "Total value in stock = #{reader.total_value_in_stock}"
# code to call
book = BookInStock.new("isbn1", 33.80)
puts "Price = #{book.price}"
puts "Price in cents = #{book.price_in_cents}"
book.price_in_cents = 1234
puts "Price = #{book.price}"
puts "Price in cents = #{book.price_in_cents}"
book_in_stock.rb:
class BookInStock
attr_reader :isbn
attr_accessor :price
def initialize(isbn, price)
#isbn = isbn
#price = Float(price)
end
def price_in_cents
Integer(price*100 + 0.5)
end
def price_in_cents=(cents)
#price = cents / 100.0
end
end
file1.csv:
ISBN,Amount
isbn1,49.00
isbn2,24.54
isbn3,33.23
isbn4,15.55
file2.csv:
ISBN,Amount
isbn5-file2,39.98
isbn6-file2,14.84
isbn7-file2,43.63
isbn8-file2,25.55
Now run the program:
~/ruby_programs$ ruby test_code.rb file1.csv file2.csv
Processing file1.csv
Processing file2.csv
Total value = 246.32
Total value in stock = 246.32
Price = 33.8
Price in cents = 3380
Price = 12.34
Price in cents = 1234
require searches for files in Ruby's load path (this is stored in the global variables $: or $LOAD_PATH)
The current directory is not in the load path by default (it used to be in ruby 1.8 and earlier) which is why ruby says that it can't find csv-reader
You can add to the load path either by manipulating the $: variable (it behaves just like an array) or with the the -I option.
For example if you launch irb by doing
irb -I.
Then your code should run without modification (assuming there are no other problems with it)
Lastly you could switch your require statements to use require_relative - this locates files relative to the current file
I have constructed an Event Manager class that performs parsing actions on a CSV file, and produces html letters using erb. It is part of a jumpstart labs tutorial
The program works fine, but I am unable to call multiple methods on an object without the earlier methods interfering with the later methods. As a result, I have opted to create multiple objects to call instance methods on, which seems like a clunky inelegant solution. Is there a better way to do this, where I can create a single new object and call methods on it?
Like so:
eventmg = EventManager.new("event_attendees.csv")
eventmg.print_valid_phone_numbers
eventmg_2 = EventManager.new("event_attendees.csv")
eventmg_2.print_zipcodes
eventmg_3 = EventManager.new("event_attendees.csv")
eventmg_3.time_targeter
eventmg_4 = EventManager.new("event_attendees.csv")
eventmg_4.day_of_week
eventmg_5 = EventManager.new("event_attendees.csv")
eventmg_5.create_thank_you_letters
The complete code is as follows
require 'csv'
require 'sunlight/congress'
require 'erb'
class EventManager
INVALID_PHONE_NUMBER = "0000000000"
Sunlight::Congress.api_key = "e179a6973728c4dd3fb1204283aaccb5"
def initialize(file_name, list_selections = [])
puts "EventManager Initialized."
#file = CSV.open(file_name, {:headers => true,
:header_converters => :symbol} )
#list_selections = list_selections
end
def clean_zipcode(zipcode)
zipcode.to_s.rjust(5,"0")[0..4]
end
def print_zipcodes
puts "Valid Participant Zipcodes"
#file.each do |line|
zipcode = clean_zipcode(line[:zipcode])
puts zipcode
end
end
def clean_phone(phone_number)
converted = phone_number.scan(/\d/).join('').split('')
if converted.count == 10
phone_number
elsif phone_number.to_s.length < 10
INVALID_PHONE_NUMBER
elsif phone_number.to_s.length == 11 && converted[0] == 1
phone_number.shift
phone_number.join('')
elsif phone_number.to_s.length == 11 && converted[0] != 1
INVALID_PHONE_NUMBER
else
phone_number.to_s.length > 11
INVALID_PHONE_NUMBER
end
end
def print_valid_phone_numbers
puts "Valid Participant Phone Numbers"
#file.each do |line|
clean_number = clean_phone(line[:homephone])
puts clean_number
end
end
def time_targeter
busy_times = Array.new(24) {0}
#file.each do |line|
registration = line[:regdate]
prepped_time = DateTime.strptime(registration, "%m/%d/%Y %H:%M")
prepped_time = prepped_time.hour.to_i
# inserts filtered hour into the array 'list_selections'
#list_selections << prepped_time
end
# tallies number of registrations for each hour
i = 0
while i < #list_selections.count
busy_times[#list_selections[i]] += 1
i+=1
end
# delivers a result showing the hour and the number of registrations
puts "Number of Registered Participants by Hour:"
busy_times.each_with_index {|counter, hours| puts "#{hours}\t#{counter}"}
end
def day_of_week
busy_day = Array.new(7) {0}
d_of_w = ["Monday:", "Tuesday:", "Wednesday:", "Thursday:", "Friday:", "Saturday:", "Sunday:"]
#file.each do |line|
registration = line[:regdate]
# you have to reformat date because of parser format
prepped_date = Date.strptime(registration, "%m/%d/%y")
prepped_date = prepped_date.wday
# adds filtered day of week into array 'list selections'
#list_selections << prepped_date
end
i = 0
while i < #list_selections.count
# i is minus one since days of week begin at '1' and arrays begin at '0'
busy_day[#list_selections[i-1]] += 1
i+=1
end
#busy_day.each_with_index {|counter, day| puts "#{day}\t#{counter}"}
prepared = d_of_w.zip(busy_day)
puts "Number of Registered Participants by Day of Week"
prepared.each{|date| puts date.join(" ")}
end
def legislators_by_zipcode(zipcode)
Sunlight::Congress::Legislator.by_zipcode(zipcode)
end
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
def create_thank_you_letters
puts "Thank You Letters Available in Output Folder"
template_letter = File.read "form_letter.erb"
erb_template = ERB.new template_letter
#file.each do |line|
id = line[0]
name = line[:first_name]
zipcode = clean_zipcode(line[:zipcode])
legislators = legislators_by_zipcode(zipcode)
form_letter = erb_template.result(binding)
save_thank_you_letters(id,form_letter)
end
end
end
The reason you're experiencing this problem is because when you apply each to the result of CSV.open you're moving the file pointer each time. When you get to the end of the file with one of your methods, there is nothing for anyone else to read.
An alternative is to read the contents of the file into an instance variable at initialization with readlines. You'll get an array of arrays which you can operate on with each just as easily.
"Is there a better way to do this, where I can create a single new object and call methods on it?"
Probably. If your methods are interfering with one another, it means you're changing state within the manager, instead of working on local variables.
Sometimes, it's the right thing to do (e.g. Array#<<); sometimes not (e.g. Fixnum#+)... Seeing your method names, it probably isn't.
Nail the offenders down and adjust the code accordingly. (I only scanned your code, but those Array#<< calls on an instance variable, in particular, look fishy.)