Start

associative_arrays.rb

@@ -0,0 +1,5 @@
+aa = [ %w[Someone 1],
+      %w[Bla 2]]
+
+p aa.assoc("Someone")
+p aa.assoc("Bla")

autovivification.rb

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+deep = Hash.new { |hash,key| hash[key] = Hash.new(&hash.default_proc) }
+
+
+deep[:a][:b][:c][:d] = 42
+p deep

blocks_can_take_blocks.rb

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+var = :var
+object = Object.new
+
+object.define_singleton_method(:show_var_and_block) do |&block|
+  p [var, block]
+end
+
+object.show_var_and_block { :block }

bubbling_up_thread_errors.rb

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+Thread.abort_on_exception = true
+
+Thread.new do
+  fail 'Ops, we cannot continue'
+end
+
+loop do
+  sleep
+end

case_on_ranges.rb

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+age = rand(1..100)
+p age
+
+case age
+  when -Float::INFINITY..20
+    p 'You are too young'
+  when 21..64
+    p 'You are at the right age'
+  when 65..Float::INFINITY
+    p 'You are too old'
+end

count_all_objects.rb

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+require 'pp'
+
+pp ObjectSpace.count_objects

cycle.rb

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+ring = %w[one two three].cycle
+
+p ring.take(5)

data.rb

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+puts DATA.read
+
+__END__
+Hey oh!
+Hey oh!

easiest_database_pstore.rb

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+require 'pstore'
+
+db = PStore.new('mydatabase.pstore')
+
+db.transaction do
+  db['people1'] = 'Someone'
+  db['money1'] = 400
+end
+
+db.transaction do
+  db['people2'] = 'Someone2'
+  db['money2'] = 300
+end
+
+
+db.transaction(true) do
+  p 'People %p' % db['people1']
+  p 'Money %p' % db['money1']
+  p "SECOND PERSON"
+  p 'People %p' % db['people2']
+  p 'Money %p' % db['money2']
+end

easiest_database_pstore_yaml.rb

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+require 'yaml/store'
+
+db = YAML::Store.new('people.yml')
+
+db.transaction do
+  db['people1'] = 'Someone'
+  db['money1'] = 400
+end
+
+db.transaction do
+  db['people2'] = 'Someone2'
+  db['money2'] = 300
+end
+
+
+db.transaction(true) do
+  p 'People %p' % db['people1']
+  p 'Money %p' % db['money1']
+  p "SECOND PERSON"
+  p 'People %p' % db['people2']
+  p 'Money %p' % db['money2']
+end

email.txt

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+#! /usr/bin/env ruby -w
+
+puts "This is one email"
+
+__END__

enable_ruby_warnings.rb

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+$VERBOSE = true
+
+class WarnMe
+  def var
+    @var || 42
+  end
+end
+
+
+p WarnMe.new.var
+

fast_memoization_fibonacci.rb

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+fibonacci = Hash.new{ |numbers,index|
+  numbers[index] = fibonacci[index - 2] + fibonacci[index - 1]
+}.update(0 => 0, 1 => 1)
+
+
+p fibonacci[300]

fetch_data.rb

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+params = {var: 42}
+
+p params.fetch(:var)
+p params.fetch(:missing, 42)
+p params.fetch(:missing) { 40 + 2 }
+
+params.fetch(:missing)
+

get_random_data.rb

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+require 'securerandom'
+
+p SecureRandom.random_number
+p SecureRandom.random_number(100)
+p
+p SecureRandom.hex(20)
+p SecureRandom.base64(20)

inject.rb

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+p (1..10).inject{ |r,e| p [r,e]; r*2}
+

inspecting_the_source_with_script_lines.rb

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+SCRIPT_LINES__ = { }
+
+#require_relative = 'better_be_well_formed_code'
+require_relative = 'better_be_well_formed_code_with_a_line_size_greather_than_80_it_is_not_good'
+
+if SCRIPT_LINES__.values.flatten.any? { |line| line.size > 80}
+  abort 'Clean up your code first!'
+end

iterating_over_specific_types.rb

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+ObjectSpace.each_object(String) do |object|
+  p object
+end

lambda_your_own_syntax.rb

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+# encoding UTF-8
+
+module Kernel
+  alias_method :λ, :lambda
+end
+
+l = λ { p :called }
+l.call

people.yml

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+---
+people1: Someone
+money1: 400
+people2: Someone2
+money2: 300

print_formatted_with_debug.rb

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+def debug(name, content)
+  p "%s:  %p" % [name, content]
+end
+
+debug "Num", 42
+

ruby_can_even_explain_it_to_you.txt

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+ruby -e 'puts { is_this_a_block }' --dump parsetree
+ruby -e 'puts { is_this_a_block }' --dump parsetree_with_comment

ruby_debug_flag.rb

@@ -0,0 +1,9 @@
+def var
+  @var || 40
+end
+
+if $DEBUG
+  p "var is %p" % var
+end
+
+p var + 2

shortcut_variable_interpolation.rb

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+@instance = :instance
+@@class = :class
+$global = :global
+
+p "#@instance, #@@class, and #$global variables don't need braces"

single_instance_running.rb

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+DATA.flock(File::LOCK_EX | File::LOCK_NB) or abort 'Already running'
+
+trap('INT', 'EXIT')
+puts 'Running...'
+loop do
+  sleep
+end
+
+__END__
+DO NOT DELETE: used for locking

struct_without_assignment.rb

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+Struct.new("Name", :first, :last) do
+  def full
+    "#{first} #{last}"
+  end
+end
+
+franzejr = Struct::Name.new("Franze", "Jr")
+p franzejr.full

super_magic_key_word.rb

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+class Parent
+  def show_args(*args)
+    p args
+  end
+end
+
+class Child < Parent
+  def show_args(a,b,c)
+    super(a,b,c)
+  end
+end
+
+Child.new.show_args(:a, :b, :c)

super_magic_key_word2.rb

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+class Parent
+  def show_args(*args, &block)
+    p [*args, block]
+  end
+end
+
+class Child < Parent
+  def show_args(a,b,c)
+    super
+  end
+end
+
+#Everything goes up, including the block
+Child.new.show_args(:a, :b, :c) { :block }

super_magic_key_word3.rb

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+class Parent
+  def show_args(*args, &block)
+    p [*args, block]
+  end
+end
+
+class Child < Parent
+  def show_args(a,b,c)
+    #modify super by passing nothing
+    super()
+  end
+end
+
+#Nothing goes up
+Child.new.show_args(:a, :b, :c)

super_magic_key_word4.rb

@@ -0,0 +1,15 @@
+class Parent
+  def show_args(*args, &block)
+    p [*args, block]
+  end
+end
+
+class Child < Parent
+  def show_args(a,b,c)
+    #modify super by passing nothing
+    super(&nil)
+  end
+end
+
+#Nothing goes up, neither the block
+Child.new.show_args(:a, :b, :c) { :block }

super_magic_key_word5.rb

@@ -0,0 +1,15 @@
+class DontDelegateToMe; end
+class DelegateToMe; def delegate; "DelegateToMe" end end
+
+module DelegateIfCan
+  def delegate
+    if defined? super
+      "Modified:  #{super}"
+    else
+      "DelegateIfCan"
+    end
+  end
+end
+
+p DelegateToMe.new.extend(DelegateIfCan).delegate
+p DontDelegateToMe.new.extend(DelegateIfCan).delegate

tail_call.rb

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+RubyVM::InstructionSequence.compile_option = { tailcall_optimization: true,
+                                               trace_instruction: false }
+
+eval <<end
+  def factorial(n, result=1)
+    if n==1
+      result
+    else
+      factorial(n-1, n*result)
+    end
+  end
+end
+
+p factorial(100000)

trigger_irb_as_needed.rb

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+require 'irb'
+
+def my_program_context
+  @my_program_context ||= Struct.new(:value).new(40)
+end
+
+trap(:INT) do
+  IRB.start
+  trap(:INT, 'EXIT')
+end
+
+loop do
+  p "Current value: #{my_program_context.value}"
+  sleep 1
+end

turn_on_garbage_collector.rb

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+GC::Profiler.enable
+
+10.times do
+  array = Array.new(1_000_000) { |i| i.to_s }
+end
+
+p GC::Profiler.result

unused_variable_format.rb

@@ -0,0 +1,7 @@
+  [
+    ['Someone', 41, 'another field'],
+    ['Someone2', 42, 'another field2'],
+    ['Someone3', 43, 'another field3']
+  ].each do |name,_,_|
+    p name
+  end

variables_from_a_regex.rb

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+if  /\A(?<first>\w+),\s*(?<last>\w+)\z/ =~ "Franze, Jr"
+  puts "#{first} #{last}"
+end

zip.rb

@@ -0,0 +1,6 @@
+letters = "a".."d"
+numbers = 1..3
+
+letters.zip(numbers) do |letter, number|
+  p(letter: letter, number: number)
+end