1. Ruby

2. What is Ruby? Programming Language Object-oriented Interpreted Popular- Ruby on Rails a framework for Web Server Programming

3. Interpreted Languages Not compiled like Java Code is written and then directly executed by an interpreter Type commands into interpreter and see immediate results Computer Runtime Environment CompilerCode Java: ComputerInterpreterCode Ruby:

4. What is Ruby on Rails (RoR) Development framework for web applications written in Ruby Used by some of your favorite sites!favorite sites

5. Advantages of a framework Standard features/functionality are built-in Predictable application organization Easier to maintain Easier to get things going

6. Installation Windows Navigate to: http://www.ruby-lang.org/en/downloads/http://www.ruby-lang.org/en/downloads/ Scroll down to "Ruby on Windows" Download the "One-click Installer" Follow the install instructions Include RubyGems if possible (this will be necessary for Rails installation later) Mac/Linux OS X 10.4 ships with broken Ruby! Go here… http://hivelogic.com/articles/view/ruby-rails-mongrel-mysql-osx

7. hello_world.rb puts "hello world!" All source code files end with.rb = ruby NOTE: we are not really going to learn how to make general ruby programs but, in this class we will learn about Ruby on Rails ---which is a web framework for making web apps or web sites.

8. puts vs. print "puts" adds a new line after it is done analogous System.out.println() "print" does not add a new line analogous to System.out.print()

9. Running Ruby Programs (via interpreter) Use the Ruby interpreter ruby hello_world.rb “ruby” tells the computer to use the Ruby interpreter Interactive Ruby (irb) console irb Get immediate feedback Test Ruby features NOTE: we are not really going to learn how to make general ruby programs but, in this class we will learn about Ruby on Rails --- which is a web framework for making web apps or web sites.

10. Comments # this is a single line comment =begin this is a multiline comment nothing in here will be part of the code =end

11. Variables Declaration – No need to declare a "type" Assignment – same as in Java Example: (like javascript) x = "hello world"# String y = 3# Fixnum z = 4.5# Float r = 1..10# Range

12. Variable Names and Scopes foo Local variable $foo Global variable @foo Instance variable in object @@foo Class variable MAX_USERS “Constant” (by convention)

13. Difference between instance and “class” variables Instance variables are scoped within a specific instance. instance variable title, each post object will have its own title. Class variables, instead, is shared across all instances of that class. class Post def initialize(title) @title = title end def title @title end p1 = Post.new("First post") p2 = Post.new("Second post") p1.title # => "First post" p2.title # => "Second post" class Post @@blog = "The blog“ # previous stuff for title here……. def blog @@blog end def blog=(value) @@blog = value end p1.blog # => "The blog" p2.blog # => "The blog“ p1.blog = "New blog" p1.blog # => "New blog" p2.blog # => "New blog"

14. Objects Everything is an object. Common Types (Classes): Numbers, Strings, Ranges nil, Ruby's equivalent of null is also an object Uses "dot-notation" like Java objects You can find the class of any variable x = "hello" x.class  String You can find the methods of any variable or class x = "hello" x.methods String.methods

15. String Literals “How are you today?”

16. Single quotes (only \' and \\ ) 'Bill\'s "personal" book' Double quotes (many escape sequences) "Found #{count} errors\nAborting job\n" %q (similar to single quotes) %q Hello > %Q (similar to double quotes) %Q|She said "#{greeting}"\n| “Here documents” <<END First line Second line END Ruby String Syntax

17. Equalities

18. x = Array.new # how to declare an array x << 10 x[0] = 99 y = ["Alice", 23, 7.3] x[1] = y[1] + y[-1] ary = Array.new #sets to empty array [] Array.new(3) #sets to length of 3 [nil, nil, nil] Array.new(3, true) #sets to length of 3 [true, true, true] person = Hash.new person["last_name"] = "Rodriguez" person[:first_name] = "Alice“ order = {"item" => "Corn Flakes", "weight" => 18} order = {:item => "Corn Flakes", :weight => 18} order = {item: "Corn Flakes", weight: 18} Arrays and Hashes

19. Hashes – Starting the Zombies example From http://railsforzombies.org/http://railsforzombies.org/

20. Arrays ---accessing elements arr = [1, 2, 3, 4, 5, 6] arr[2] # 3 arr[100] # nil arr[-3]# 4 arr[2, 3] # [3, 4, 5] –means start index 2 and get 3 elements arr[1..4] # [2, 3, 4, 5] –means start index 1 through 4 index Also, arr.first and arr.last array = [14, 22, 34, 46, 92] for value in array do... end

21. Objects (cont.) There are many methods that all Objects have Include the "?" in the method names, it is a Ruby naming convention for boolean methods nil? eql?/equal? ( 3.eql?2 ) ==, !=, === instance_of? is_a? to_s

22. Numbers Numbers are objects Different Classes of Numbers FixNum, Float 3.eql?2  false -42.abs  42 3.4.round  3 3.6.round  4 3.2.ceil  4 3.8.floor  3 3.zero?  false

23. Boolean nil or false = false Everything else = true

24. String Methods "hello world".length  11 "hello world".nil?  false "".nil?  false "ryan" > "kelly"  true "hello_world!".instance_of?String  true "hello" * 3  "hellohellohello" "hello" + " world"  "hello world" "hello world".index("w")  6

25. Operators and Logic Same as Java *, /, +, - Also same as Java "and" and "or" as well as "&&" and "||" Strings String concatenation (+) String multiplication (*)

26. Conditionals: if/elsif/else/end Must use "elsif" instead of "else if" Notice use of "end". It replaces closing curly braces in Java Example: if (age < 35) puts "young whipper-snapper" elsif (age < 105) puts "80 is the new 30!" else puts "wow… gratz..." end

27. Inline "if" statements Original if-statement if age < 105 puts "don't worry, you are still young" end Inline if-statement puts "don't worry, you are still young" if age < 105

28. Case Statements grade = case score when 0..60: ‘F’ when 61..70: ‘D’ when 71..80: ‘C’ when 81..90: ‘B’ when 90..100: ‘A’ end

29. for-loops for-loops can use ranges Example 1: for i in 1..10 puts i end

30. for-loops and ranges You may need a more advanced range for your for-loop Bounds of a range can be expressions Example: for i in 1..(2*5) puts i end

31. Out of blocks or loops: break, redo, next, retry

32. while-loops Cannot use "i++" Example: i = 0 while i < 5 puts i i = i + 1 end

33. Example little routine sum = 0 i = 1 while i <= 10 do sum += i*i i = i + 1 end puts "Sum of squares is #{sum}\n" Newline is statement separator do... end instead of {... } Optional parentheses in method invocation Substitution in string value No variable declarations

34. unless "unless" is the logical opposite of "if" Example: unless (age >= 105)# if (age < 105) puts "young." else puts "old." end

35. until Similarly, "until" is the logical opposite of "while" Can specify a condition to have the loop stop (instead of continuing) Example i = 0 until (i >= 5) # while (i < 5), parenthesis not required puts I i = i + 1 end

36. Methods Structure def method_name( parameter1, parameter2, …) statements end Simple Example: def print_ryan puts "Ryan" end

37. Parameters No class/type required, just name them! Example: def cumulative_sum(num1, num2) sum = 0 for i in num1..num2 sum = sum + i end return sum end # call the method and print the result puts(cumulative_sum(1,5))

38. Return Ruby methods return the value of the last statement in the method, so… def add(num1, num2) sum = num1 + num2 return sum end can become def add(num1, num2) num1 + num2 end

39. Method with array as parameter def max(first, *rest) result= first for x in rest do if (x > result) then result= x end return result end

40. Modules – require one.rb file into another Modules: Grouping of methods, classes, constants that make sense together…a bit like a library

41. User Input "gets" method obtains input from a user Example name = gets puts "hello " + name + "!" Use chomp to get rid of the extra line puts "hello" + name.chomp + "!" chomp removes trailing new lines

42. Changing types You may want to treat a String a number or a number as a String to_i – converts to an integer (FixNum) to_f – converts a String to a Float to_s – converts a number to a String Examples "3.5".to_i  3 "3.5".to_f  3.5 3.to_s  "3"

43. Constants In Ruby, constants begin with an Uppercase They should be assigned a value at most once This is why local variables begin with a lowercase Example: Width = 5 def square puts ("*" * Width + "\n") * Width end

44. Handling Exceptions: Catch Throw def sample # a silly method that throws and exception x=1 throw :foo if x==1 end begin puts ‘start’ sample # call above method puts ‘end’ rescue puts ‘exception found’ end General format of handling exceptions begin # - code that could cause exception rescue OneTypeOfException # - code to run if OneTypeException rescue AnotherTypeOfException # - code to run if AnotherTypeOfException else # code to run for Other exceptions end

45. Classes

46. Slide 46 Simple Class class Point def initialize(x, y) @x = x @y = y end def x #defining class variable @x end def x=(value) @x = value end #code using class p = Point.new(3,4) puts "p.x is #{p.x}" p.x = 44

47. Another class - Book class Book def initialize(title, author, date) @title = title #various variables @author = author @date = date end def to_s#method to make string "Book: #@title by #{@author} on #{@date}" end

48. Book class—adding methods to access class variables (setter/getter) class Book def initialize(title, author, date) # constructor @title = title @author = author @date = date end def author #method to access class variable author @author end def author=(new_author) #method to set value of class variable author @author = new_author end

49. Class Inheritance (calling parent-super) class Book def initialize(title, author, date) @title = title @author = author @date = date end def to_s "Book: #@title by #{@author} on #{@date}" end class ElectronicBook < Book def initialize(title, author, date, format) super(title, author, date) @format = format end def to_s super + " in #{@format}" end

50. Protection Types –here for methos class Foo def method1 end def method2 end.... public :method1, method3 protected :method2 private :method4, method5 end Public Methods: Public methods can be called by anyone. Methods are public by default except for initialize, which is always private. Private Methods: Private methods cannot be accessed, or even viewed from outside the class. Only the class methods can access private members. Protected Methods: A protected method can be invoked only by objects of the defining class and its subclasses. Access is kept within the family.

51. Creating a method operator called < (w/test class showing using it) class Book attr_reader :title def initialize(title, author, date) @title = title @author = author @date = date end def <(book) return false if book.kind_of(Book) title < book.title end require 'test/unit' require 'book' class TestExample < Test::Unit::TestCase def test_operator cat = Book.new("Cat", "Me", "1990") dog = Book.new("Dog", "Me", "1990") assert( cat < dog) end

52. File I/O file = File.open('testFile') while line = file.gets puts line end file.close File.open('testFile') do |file| while line = file.gets puts line end File.open('testFile') do |file| file.each_line {|line| puts line} end IO.foreach('testFile') {|line| puts line} puts IO.readlines('testFile') array = IO.readlines('testFile') rread-only, start at beginning of file r+read/write, start at beginning of file wwrite-only, start at beginning of file w+read/write, start at beginning of file awrite-only, append to end of file a+read/write, start at end of file bBinary mode, Windows only, combine with above mode = 'a' File.open('testFile', mode) do |file| file.print 'cat' file.puts 'dog' file.puts 5 end File.open('testFile', mode) do |file| file << 'cat' << "dog\n" << 5 << "\n" end

53. Threads require 'net/http' pages = %w{ www.yahoo.com www.google.com slashdot.org} threads = [] for page_to_fetch in pages threads << Thread.new(page_to_fetch) do |url| browser = Net::HTTP.new(url, 80) puts "Fetching #{url}" response = browser.get('/', nil) puts "Got #{url}: #{response.message}" end threads.each {|thread| thread.join } Fetching www.yahoo.com Fetching www.google.com Fetching slashdot.org Got www.yahoo.com: OK Got www.google.com: OK Got slashdot.org: OK Note: Thread and HTTP are classes in ruby NOTE: General code to create thread & associate running code (do block) and join it to thread pool thread = Thread.new do #code to execute in Thread running end thread.join

54. References Web Sites http://www.ruby-lang.org/en/ http://rubyonrails.org/ Books Programming Ruby: The Pragmatic Programmers' Guide (http://www.rubycentral.com/book/)http://www.rubycentral.com/book/ Agile Web Development with Rails Rails Recipes Advanced Rails Recipes