My notes from the book "Eloquent Ruby by Russ Olsen"

ch1.md

Chapter 1

Every programming community quickly converges on a style, an accepted set of idioms. Programming is all about communication and knowing those idioms are key to being a successful programmer in that community.

Ruby style of programming:

• Code should be crystal clear, it should shout its intent
• Good code is also concise

Ruby indentation convention:

• 2 spaces per level
• Never use tabs to indent

Ruby comments:

• Anything following a # in the code is a comment
• Good Ruby code should speak for itself, so go easy on the comments
• Avoid boilerplate comments
• Comments explaining how to use your software are great to have
• Just so you know, multiline comments in Ruby are delimited by =begin and =end but they are hardly used
• Above all, remember that good code is like a good joke: It needs no explanation

Naming things:

• With a few notable exceptions, you should use lowercase_words_separated_by_underscores
• Exceptions include modules, classes and constants
  • Module and classes should be CamelCased
  • And constants should use UPPERCASE_WORDS_SEPARATED_BY_UNDERSCORES

Parentheses:

• Optional
  • We don't do empty argument lists
  • puts 'No parentheses'
  • We usually leave them off around the conditions in control statements
• Occasionally forbidden

Examples of having more than one statement per line:

# Example 1
puts doc.title; puts doc.author

# Example 2
class DocumentException < Exception; end

# Example 3
def no_op; end

Folding up code blocks:

• If your block consists of a single statement, fold the whole statement into a single line and delimit the block with braces.
• If you have a multi-statement block, spread the block out over a number of lines, and use the do/end form.

When formatting code, always mix in a pinch of pragmatism.

The best way to learn to write idiomatic Ruby code is to read idiomatic Ruby code.

• The Ruby Standard Library
• Set
• Little Known Ways to Ruby Mastery by James Edward Gray II
• Ruby: Designers, Producers and Consumers
  • Yukihiro 'Matz' Matsumoto
  • Dave Thomas
  • Yehuda Katz
  • Glenn Vanderburg
  • Evan Phoenix

Questions

1. When do instance variables come into scope?

See Instance Variables in Ruby.

Trying to reference an uninitialized instance variable will return nil rather than raise an exception.

@b      #=> nil
@b.nil? #=> true
@b = 5  #=> 5
@b.nil? #=> false

2. Where is the source file for set.rb located?

On my machine it's at: ~/.rvm/src/ruby-1.9.3-p429/lib/set.rb.

ch2.md

Chapter 2

The if statement is pretty standard.

def even?(n)
  if n % 2 == 0
    true
  else
    false
  end
end

# of course we can just do

n.even?

unless is used for if not statements.

while something_is_true
  do_something
end

until is used for while not statements.

Use the modifier forms where appropriate:

• do_this if that
• do_this unless that
• do_this while that
• do_this until that

Use each, not for. The for loop is really not used.

cars = ['audi', 'benz', 'cadillac', 'datsun']

# instead of this
for car in cars
  puts car
end

# do this
cars.each do |car|
  puts car
end

Remember: Only false and nil are treated as false. Ruby treats everything else as true.

Resources

• How a Ruby Case Statement Works and What You Can Do With It
• Ruby QuickRef

ch3.md

Chapter 3

Array and Hash.

ch4.md

Chapter 4

String.

ch5.md

Chapter 5

Regexp.

Resources

• Rubular - a Ruby regular expression editor and tester

ch6.md

Chapter 6

Symbol.

ch7.md

Chapter 7

Object.

ch8.md

Chapter 8

Resources

• Ruby is dynamically and strongly typed
• Martin Fowler on Dynamic Typing
• Dave Thomas on the Benefits of Dynamic Typing

ch9.md

Chapter 9

Write thoroughly comprehensible tests if you can, write sketchy tests if you must, but write the tests.

Resources

• MiniTest
• RSpec

reading.md

Good Code to Read

• Set
• ActiveSupport::HashWithIndifferentAccess

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Here is the Document Class from the book.