The document discusses various Ruby programming concepts including conditionals, iterators, blocks, hashes and arrays. It provides examples of how to use if/else statements, loops, iterators like each and times to iterate over collections. It also demonstrates creating and manipulating hashes and arrays through various operations and accessing values.

1. Conditionals, Iterators & Blocks With Hashes & Arrays

2. Conditionals

3. 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

4. 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”) …

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

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

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

8. Iterators

9. 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

10. 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”]

11. Accessing Array Values a = [ "a", "b", "c", "d", "e" ] a[0] #=> "a” a[2] #=> "c” a[6] #=> nil a[1, 2] #=> ["b", "c”] a[1..3] #=> ["b", "c", "d”] a[1…3] #=> ["b", "c"]

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

14. 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}

15. 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

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

17. Each superheroes = [“catwoman”, “batman”, “wonderwoman”] superheroes.each { | s | puts “#{ s } save me!” } wonderwoman save me! batman save me! catwoman save me! dogs = ["fido", "fifi", "rex", "fluffy"] dogs_i_want = [] dogs.each { |dog| dogs_i_want.push(dog) if dog != "fluffy" } >> dogs => ["fido", "fifi", "rex", "fluffy"] >> dogs_i_want => ["fido", "fifi", "rex"]

18. Blocks

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

20. 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”

21. Block Syntax { |x| puts x} is the same as: do |x| puts x end

22. Performance Monitor: Blocks in Practice Finding the bottleneck in a slow application

23. Stubs Syntax: A.stub!(:msg).and_return(:default) A.stub!(:msg).with(1).and_return(:default)

24. Stubbing Time How can we do this to help with Time.now? t = Time.now t + 10 #adds 10 seconds Stubbing Time: Time.stub!(:now).and_return{fake_time += 10}

25. How to Use Stubs in a Test: describe “Time stub” do it “should increment mock_time by 10 seconds” do fake_time = 0 Time.stub!(:now).and_return { fake_time += 10 } Time.now.should == 10 Time.now.should == 20 end end

26. Your Turn

27. Homework Chapters: 6.1-6.3 9.1-9.3 Koans: -about_blocks -about_iteration -about_control_statements -about_array_assignment -about_arrays -about_hashes