Ruby and Rails - Session 1

Ruby and Rails course for technical people that are not Ruby developers. First session, held @ Freeletics GmbH HQ

Transcript

1. RUBY & RAILS
   

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2. GET TO KNOW RUBY
   • 1993
   
   • Japan
   
   • Matz (Matsumoto Yukihiro)
   
   • Perl, Smalltalk, Eiffel, Ada, Lisp
   
   • Scripting language
   
   • Goals: truly OO, simple syntax, GC, closures, portable
   
   • Multi paradigm (functional, OO, imperative)
   
   • Dynamically strongly typed
   
   • ~2000: Ruby 1.8 -> Duck Typing, Ruby on Rails, The Pickaxe
   Book
   
   • A favorite of Martin Fowler ;)
   

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3. “
   I hope to see Ruby help every programmer in the world
   to be productive, and to enjoy programming, and to be
   happy. That is the primary purpose of Ruby language.
   -Matz @ Google Tech Talk (2008)
   

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4. PHILOSOPHY
   • Designed to minimize work, confusion and to be enjoyable
   
   • Principles of good user interface design
   
   • Emphasize human needs over computer needs
   
   • MISWAN - Community
   

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5. “
   People are part of the system. The design should match
   the user's experience, expectations, and mental models.
   -Saltzer and Kaashoek
   “Principles of computer system design: an
   introduction“ (2009)
   

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6. POLA
   • Principle of least astonishment / surprise
   
   • Associated with Ruby, but!
   

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7. “
   Everyone has an individual background. […] The
   principle of least surprise is not for you only. The
   principle of least surprise means principle of least my
   surprise. And it means the principle of least surprise
   after you learn Ruby very well.
   -Matz in "The Philosophy of Ruby” by
   Venners (2015)
   

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8. RUBY IMPLEMENTATIONS
   • Reference implementation: MRI - Matz’s Ruby Interpreter
   a.k.a. CRuby
   
   alternatives

   • complete list https://github.com/cogitator/ruby-
   implementations/wiki/List-of-Ruby-implementations
   
   • most notable list https://www.ruby-lang.org/en/about/ in
   “Other Implementations of Ruby”
   
   • JRuby on top of JVM
   
   • Rubinius - Ruby in Ruby
   
   • mruby - embedded, led by Matz
   

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9. IRB REPL
   • Interactive Ruby Shell
   
   • Read - Eval - Print Loop
   
   • Command line tool with command history, line editing,
   network access
   

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10. BASIC SYNTAX - NAMING CONVENTIONS
    • Use English
    
    • snake_case for symbols, methods, variables
    
    • CamelCase for classes and modules (keep acronyms)
    
    • snake_case for file and directory names
    
    • Name of the file = name of the class -> One class, one file
    
    • SCREAMING_SNAKE_CASE for constants
    
    • Predicate methods end with a question mark, no prefix (ex.
    user.coach_subscription?)
    
    • Potentially dangerous methods end with an exclamation mark (a bang)
    • # comment
    • https://github.com/bbatsov/ruby-style-guide
    

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11. BASIC SYNTAX - DECLARATIONS
    • variable (local, instance, class, global)

    

    greeting = “hi”

    • method

    

    def say_hi

    puts “hi”

    end
    

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12. BASIC SYNTAX - CONTROL STRUCTURES
    if condition1
    something
    elsif condition2
    something else
    else
    finally
    end
    

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13. BASIC SYNTAX - CONTROL STRUCTURES
    if condition
    something
    end
    

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14. BASIC SYNTAX - CONTROL STRUCTURES
    something if condition
    

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15. BASIC SYNTAX - CONTROL STRUCTURES
    unless condition
    something
    else
    something else
    end
    if !condition
    something
    else
    something else
    end
    

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16. BASIC SYNTAX - CONTROL STRUCTURES
    a = 2
    case
    when a == 1, a == 2
    puts "a is one or two"
    when a == 3
    puts "a is three"
    else
    puts "I don't know what a is"
    end
    

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17. BASIC SYNTAX - LOOPS
    for i in 1..8 do
    puts i
    end
    1.upto(5) do |i|
    puts i
    end
    5.times do |i|
    puts i
    end
    

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18. BASIC SYNTAX - LOOPS
    array.each do |elem|
    puts elem
    end
    for elem in [1, 2, 3] do
    puts elem
    end
    

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19. BASIC SYNTAX - LOOPS
    i = 0
    until i == 5 do
    puts i
    i += 1
    end
    i = 0
    while i < 5 do
    puts i
    i += 1
    end
    

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20. BASIC SYNTAX - LOOPS
    puts i while i < 5
    puts i until i == 5
    

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21. DATA TYPES IN RUBY-CORE
    • Numeric: Integer, Float, Complex, Rational
    
    • Collections: Array, Hash, Range, Struct, Enumerator
    
    • Text: String, Symbol
    
    • Boolean: TrueClass, FalseClass, NilClass
    

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22. DATA TYPES - STRINGS
    "I am a string"
    'I am also a string'
    

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23. DATA TYPES - SYMBOLS
    :symbol
    :"yup still a symbol"
    "me too".to_sym
    Like a string, but instantiated only once per application execution
    

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24. DATA TYPES - SYMBOLS
    "test".object_id
    => 70308044363980
    "test".object_id
    => 70308044357840
    :test.object_id
    => 196968
    :test.object_id
    => 196968
    

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25. DATA TYPES - ARRAYS
    Initialization
    [1, "two", 3]
    Array.new() # empty
    Array.new(quantity, content)
    %w[array of only words]
    Usage
    foo = [1, "two", 3]
    foo[1] # => "two"
    

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26. DATA TYPES - HASHES
    Initialization
    {one: "value", two: 20, three: [1, 2, 3]}
    {"one" => "value", "three" => [1, 2]}
    Hash.new() # empty
    Hash.new(default) # what to return if no key
    Usage
    foo = {first: "one", two: 2}
    foo[:first] # => "one"
    foo["first"] # => nil
    

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27. HANDS ON #1
    • Anna is 38, she is from Germany, she prefers cats, earns
    40k per year, she studied Economics
    
    • Mike is 27, he is from China, he prefers dogs, earns 40k
    per year, he studied Medicine
    
    • Svetla is 35, she is from Bulgaria, she prefers cats, earns
    80k per year, she studied Electrical Engineering
    
    • Theo is 60, he is from Germany, he doesn’t like pets, earns
    50k per year, he studied Law
    
    1. Create appropriate data structures
    
    2. Find all people who are from Europe
    
    3. Find all people who earn between 45k and 70k per year
    
    4. Find all people who don’t like pets
    

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28. CREDITS
    Monica Giambitto - 2017
    
    This work is licensed under the Creative Commons
    Attribution-NonCommercial-ShareAlike 4.0 International
    License.
    
    I don't own the right to the images unless otherwise stated. If
    you feel you rights have been violated, please contact me at
    monica.giambitto@protonmail.ch
    
    To view a copy of this license visit 

    http://creativecommons.org/licenses/by-nc-sa/4.0/
    
    You can find the slides on speakerdeck.com/nirnaeth
    

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29. THANKS!
    @KFMOLLI
    GITHUB.COM/NIRNAETH
    SPEAKERDECK.COM/NIRNAETH
    

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