Ruby for Programmers, an introduction that includes conditionals, iterators and blocks

1. Ruby

2. The Ruby Language Originally by Yukihiro "Matz" Matsumoto “Ruby is designed for programmer productivity and fun, following the principles of good user interface design. He stresses that systems design needs to emphasize human, rather than computer, needs.” http://en.wikipedia.org/wiki/Ruby_(programming_language)#History Ruby 1.0 was released in 1996.

3. Ruby Language Overview Dynamically typed Interpreted Can be modified at runtime Object oriented Blocks & lambdas Nice support for Regular Expressions

4. Lets get started IRB: InteractiveRuBy >> 4 >> 4 + 4

5. Everything is an object “test”.upcase “test”.class “test”.methods

6. Everything evaluates to something 2 + 2 (2+2).zero?

7. Methods are Messages thing.do(4) thing.do 4 thing.send “do”, 4

8. Operators are Methods thing.do 4 thing.do(4) thing.send “do”, 4 1 + 2 1.+(2) 1.send "+", 2

9. Write your first Ruby class

10. Conditionals, Iterators & Blocks With Hashes & Arrays

11. Conditionals

12. Conditionals: if if age > 17 puts “can vote” end if age > 17 puts “can vote” else puts “attends school” end Statement Modifiers: y = 7 if x == 4 Other Syntax: if x == 4 then y = 7 end

13. Truth Truth: Everything is true except for: false nil Therefore 0 is true “” is true Checking for false: if !(name == “superman”) … if not (name == “superman”) …

14. Unless “unless” provides us with another way of checking if a condition is false: unless superpower == nil status = “superhero” end

15. Case case superhero when “superman” city = “metropolis” when “batman” city = “gotham_city” else city = “central_city” end

16. Case Refactoring city = case superhero when “superman” “metropolis” when “batman” “gotham_city” else “central_city” end

17. Iterators

18. Iterators: Conditional Looping “while” allows us to loop through code while a set condition is true x = 1 while x < 10 puts x.to_s + “ iteration” x += 1 end

19. Creating a new array x = [1, 2, 3, 4] => [1, 2, 3, 4] x = %w(1 2 3 4) => [“1”, “2”, “3”, “4”] chef = Array.new(3, “bork”) => [“bork”, “bork”, bork”]

20. Accessing Array Values a = [ "a", "b", "c", "d", "e" ] a[0] #=> "a” a[2] #=> "c” a[6] #=> nil

21. Creating a Hash h = { "a" => 100, "b" => 200 } h[“a”] h = { 1 => “a”, “b” => “hello” } h[1]

22. Operations on Hashes: Merge h1 = { "a" => 100, "b" => 200 } => {"a"=>100, "b"=>200} h2 = { "b" => 254, "c" => 300 } =>{"b"=>254, "c"=>300} h3 = h1.merge(h2) => {"a"=>100, "b"=>254, "c"=>300} h1 => {"a"=>100, "b"=>200} h1.merge!(h2) => {"a"=>100, "b"=>254, "c"=>300}

23. Operations on Hashes h = { "a" => 100, "b" => 200 } h.delete("a”) h = { "a" => 100, "b" => 200, "c" => 300, "d" => 400 } letters = h.keys h = { "a" => 100, "b" => 200, "c" => 300 } numbers = h.values

24. Times 5.times{ puts “hello” } 99.times do |beer_num| puts "#{beer_num} bottles of beer” end

25. Each superheroes = [“catwoman”, “batman”, “wonderwoman”] superheroes.each do | s | puts “#{ s } save me!” end wonderwoman save me! batman save me! catwoman save me!

26. Blocks

27. Blocks def dos_veces yield yield end dos_veces { puts "Hola” } Hola Hola Yield executes the block This is a Block! {

28. Yield with Parameters def bands yield(“abba”, “who”) end bands do |x,y| puts x,y end abba who Yield sends its parameters as arguments to the block yield(“abba”, ”who”) sends “abba” and “who” to |x, y| x is set to “abba” y is set to “who”

29. Mr. Neighborly's Humble Little Ruby BookJeremy McAnally The Well-Grounded RubyistCovering Ruby 1.9David A. Black Ruby Koansa walk along the path to enlightenmenthttp://github.com/edgecase/ruby_koans