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# Before:
class Product < ActiveRecord::Base
  has_many :purchases
end

class Purchase < ActiveRecord::Base
  belongs_to :product

  # We don't want the receipt responsibilities in Purchase
  def has_receipt?

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2014-03-20

Line 1
Line 2

2014-03-21

Line 1
Line 2

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##
# Helpers for randomized person testing.
module PersonsHelper
  ##
  # Generate the next n elements for the array, but in a predefined manner.
  class FakeElementGenerator
    ##
    # Generate elements, the first of which must be start_with.
    def initialize(start_with:)
      @start = start_with

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require 'rspec'

def sum(numbers)
  numbers.inject(0) { |sum, number| sum + number }
end

def product(numbers)
  numbers.inject(1) { |sum, number| sum * number }
end

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Resolving dependencies...
cabal: Could not resolve dependencies:
trying: yosog-0.0.0 (user goal)
rejecting: yosog-0.0.0:!test (global constraint requires opposite flag
selection)
trying: yosog-0.0.0:*test
trying: yesod-test-1.4.3.1 (dependency of yosog-0.0.0:*test)
trying: HUnit-1.2.5.2 (dependency of yesod-test-1.4.3.1)
trying: yesod-static-1.4.0.4 (dependency of yosog-0.0.0)
trying: cryptohash-conduit-0.1.1 (dependency of yesod-static-1.4.0.4)

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Answer to Question 1:

The method shown is inject, (aka reduce).

I love inject, and you should too!

Jay Fields loves inject so much he wrote a love letter to it.

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Answer to Question 2:

The syntax shown is for required keyword arguments.

Here's an example:

def foo(bar:)
  puts bar
end

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Answer to Question 3:

That's a decorator, yo!

I want to read more about decorators.

I want to watch a video where someone teaches me about decorators.

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Answer to Question 3

Sure! Symbol-to-proc is what you want here:

users.select(&:admin?)

Note that we couldn't use this if admin? took an argument, which is kind of a bummer.

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commit 81a9375d4ecbd37ca9da7efaebbffa8cf150d6f6
Author: Ben Orenstein <ben.orenstein@gmail.com>
Date:   Wed Jul 22 12:02:43 2015 -0400

    code review ideas

diff --git a/app.rb b/app.rb
index 93bac6c..c9443f6 100644
--- a/app.rb
+++ b/app.rb