tricks from jeg2 talk

gistfile1.rb

p (1..10).inject(:*) # instead of: inject(&:*)

# case on ranges
age = rand(1..100)
p age
case age
when -Float::INFINITY..20
  puts "You're too young."
when 21..64

# case on date ranges

           require "date"
          start_of_aloha_ruby_conf = Date.new(2012, 10, 8)
          end_of_aloha_ruby_conf   = Date.new(2012, 10, 9)
          case Date.today
          when Date.new...start_of_aloha_ruby_conf
            puts "Anticipation is building."
          when start_of_aloha_ruby_conf..end_of_aloha_ruby_conf
            puts "Mind being blown."
          when (end_of_aloha_ruby_conf + 1)..Date::Infinity
            puts "You've learned some Ruby while in paradise."
          end

# case on lambdas

require "prime"
n = rand(1..10)
pn
case n
when lambda(&:prime?)
  puts "This number is prime."
when l

# variables from regex
if /\A(?<last>\w+),\s*(?<first>\w+)\z/ =~ "Gray, James"
  puts "#{first} #{last}"
end

# cycle through an array
ring = %w[one two three].cycle
puts ring.take(4)

# one
# two
# three
# one

# indexing into a string with regex

str = "Price $24.95"
p str[/\$\d+(?:\.\d+)?/]
p str[/\$(\d+)(?:\.\d+)?/,           1]
p str[/\$(?<dollars>\d+)(?:\.\d+)?/, :dollars]

# find last match
expression = "40 + 2 = 42"
p expression[expression.rindex(/\d+/)..-1]
p expression[expression.rindex(/\b\d+/)..-1]

# iterating in lockstep
letters = "a".."d"
numbers = 1..3
letters.zip(numbers) do |letter, number|
  p(letter: letter, number: number)
end

#{:letter=>"a", :number=>1}
#{:letter=>"b", :number=>2}
#{:letter=>"c", :number=>3}
#{:letter=>"d", :number=>nil}

# partition

Person = Struct.new(:name, :gender)
people = [ Person.new("James",  :male),
           Person.new("Dana",   :female),
           Person.new("Summer", :female) ]
males, females = people.partition { |person| person.gender == :male }
puts "Males:",   males.map   { |male|   "  #{male.name}"   }
puts "Females:", females.map { |female| "  #{female.name}" }

# chunk your data

    headings = [ "1.1 Compiler Tricks",
                 "1.2 Syntax",
                 "1.3 Data Structures",
                 "1.4 Iterators",
                 "2.1 Core Ruby",
                 "2.2 The Standard Library",
                 "2.3 Tools",
"2.4 Black Magic" ] headings.chunk { |heading| heading[/\A\d+/] } .each do |chapter, headings|
      puts "Chapter #{chapter}:"
      puts headings.map { |heading| "  #{heading}" }
    end

# add with_index to any iterator
votes = { "Josh"  => %w[SBPP  POODR GOOS],
          "Avdi"  => %w[POODR SBPP  GOOS],
          "James" => %w[POODR GOOS  SBPP],
          "David" => %w[GOOS  SBPP  POODR],
          "Chuck" => %w[GOOS  POODR SBPP] }
tally = Hash.new(0)
votes.values.each do |personal_selections|
  personal_selections.each_with_object(tally).with_index do |(vote, totals), i|
    totals[vote] += personal_selections.size - i
end end
p tally

# struct without assignment

# instead of:  class Name < Struct.new(:first, :last) ... end
Struct.new("Name", :first, :last) do
  def full
    "#{first} #{last}"
  end
end
james = Struct::Name.new("James", "Gray")
puts james.full

# between
p 2.between?(1, 10)
p "cat".between?("bat", "rat")

# line by line reading
File.foreach(__FILE__) do |line|
  p line
end

# easiest way to read from the internet
require "open-uri"
open("http://rubyrogues.com/feed/") do |feed|
  puts feed.read.scan(%r{<title>(\d+\s*RR\b[^<]*)</title>})
end

# OO file interface
              require "pathname"
# build paths
dir = Pathname.pwd # or Pathname.new(...) path = dir + __FILE__ # add paths
              # work with paths
              puts path.realpath
              puts path.relative_path_from(dir)
              puts
              # use paths to do work
              path.open do |io|
                5.times do
                 puts io.gets
                end 
              end

# the world's easiest database
require 'pstore'
db = PStore.new("accounts.pstore")
                db.transaction do
                  db["james"] = 100.00
                  db["dana"]  = 100.00
end
                db.transaction do
                  db["dana"]  += 200.00
                  db["james"] -= 200.00
                  db.abort if db["james"] < 0.0
end
                db.transaction(true) do
                  puts "James:  %p" % db["james"]
                  puts "Dana:   %p" % db["dana"]
end