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RUBY Getting Started DANIEL MORRISON Ι COLLECTIVE IDEA APPFORUM Americas 2012

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WELCOME Daniel Morrison • @danielmorrison • Founder, Collective Idea • Based in Holland, Michigan • Programmer • Ruby & Rails Instructor

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RUBY Language • Dynamic • Object-Oriented • Designed for Programmer Productivity Ruby on Rails • Web Framework • Launched Ruby into the public eye • Inspiration for many other frameworks RhoMobile • Uses Ruby to bridge devices • Rhodes framework takes cues from Rails

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CORE RUBY

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DATA TYPES Numbers • Integer types: • 5.class #=> Fixnum • 9999999999999999999.class # => Bignum

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DATA TYPES Numbers • Integer types: • 5.class #=> Fixnum • 9999999999999999999.class # => Bignum Arithmetic Operation • + add • - subtract • * multiply • / divide • % modulus • ** exponent

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STRINGS Strings in ruby • “Hello World” • Can use single or double quoted. • As well as more esoteric syntaxes: %q|Hello World|

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STRINGS Strings in ruby • “Hello World” • Can use single or double quoted. • As well as more esoteric syntaxes: %q|Hello World| String Interpolation • “There are #{24 * 7} hours in a week.” • Only works with double quotes.

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METHODS

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METHODS Methods in ruby • Called Functions in other languages Define and call • def my_addition(value1, value2) value1 + value2 end • my_add(10, 5) # => 15

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VARIABLES

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VARIABLES Define a variable • a = “Hello World” • No need to specify type • Can redefine at any time • a = 15

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VARIABLES Define a variable • a = “Hello World” • No need to specify type • Can redefine at any time • a = 15 Strong Dynamic Typing • Strong: variable always has an explicit type • Dynamic: type can change at any time

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VARIABLES Define a variable • a = “Hello World” • No need to specify type • Can redefine at any time • a = 15 Strong Dynamic Typing • Strong: variable always has an explicit type • Dynamic: type can change at any time Duck Typing • def my_addition(value1, value2) value1 + value2 end • my_addition(“Hello”, “World”) # => “HelloWorld”

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COLLECTION DATA TYPES

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ARRAY Easy to create • a = [5, 10, 45, 9] • a = Array.new(5, 10, 45, 9) # works, but not usually used.

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ARRAY Easy to create • a = [5, 10, 45, 9] • a = Array.new(5, 10, 45, 9) # works, but not usually used. Easy to access & modify • a[2] # => 45 • a[0] = 1000 # => [1000, 10, 45, 9]

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ARRAY Easy to create • a = [5, 10, 45, 9] • a = Array.new(5, 10, 45, 9) # works, but not usually used. Easy to access & modify • a[2] # => 45 • a[0] = 1000 # => [1000, 10, 45, 9] Polyglot • b = [“banana”, 3.14, -200, “Hello World”] • Mix & match values

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ARRAY Easy to create • a = [5, 10, 45, 9] • a = Array.new(5, 10, 45, 9) # works, but not usually used. Easy to access & modify • a[2] # => 45 • a[0] = 1000 # => [1000, 10, 45, 9] Polyglot • b = [“banana”, 3.14, -200, “Hello World”] • Mix & match values Dynamically Sized • fruits = [“Apple”, “Banana”] • fruits[2] = “Orange” # => [“Apple”, “Banana”, “Orange] • fruits.length # => 3

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HASH Key-Value Store • AKA: HashTable, Dictionary, associative array • Key is unique

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HASH Key-Value Store • AKA: HashTable, Dictionary, associative array • Key is unique Easy to Create • h = {“name” => “Daniel”, “language” => “Ruby”}

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HASH Key-Value Store • AKA: HashTable, Dictionary, associative array • Key is unique Easy to Create • h = {“name” => “Daniel”, “language” => “Ruby”} Easy to Access • Array-like syntax • h[“name”] # => “Daniel” • h[“age”] # => nil • h[“age”] = 10 # => {“name” => “Daniel”, “age => 10, “language” => “Ruby”}

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HASH Key-Value Store • AKA: HashTable, Dictionary, associative array • Key is unique Easy to Create • h = {“name” => “Daniel”, “language” => “Ruby”} Easy to Access • Array-like syntax • h[“name”] # => “Daniel” • h[“age”] # => nil • h[“age”] = 10 # => {“name” => “Daniel”, “age => 10, “language” => “Ruby”} Symbols • Begin with a colon • Most often used as hash keys • h = {:name => “Alice”, :age => 10} • h[:age] # => 10 • h[“age”] # => nil

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NESTING Both Hash & Array can contain each other • apple = {“name” => “Apple”, “colors” => [“red”, “green”]} • banana = {“name” => “Banana”, “colors” => [“yellow”]} • fruits = [apple, banana] • fruits.last # => {“name” => “Banana”, “colors” => [“yellow”]}

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NESTING Both Hash & Array can contain each other • apple = {“name” => “Apple”, “colors” => [“red”, “green”]} • banana = {“name” => “Banana”, “colors” => [“yellow”]} • fruits = [apple, banana] • fruits.last # => {“name” => “Banana”, “colors” => [“yellow”]} Multidimensional Arrays • matrix = [[3, 2, 6], [1, 4, 5], [7, 4, 7]] • matrix[0] # => [3, 2, 6]

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RANGE Ranges of values • r = (10..100) • r.include?(20) # => true • r.include?(2) # => false

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RANGE Ranges of values • r = (10..100) • r.include?(20) # => true • r.include?(2) # => false Useful with Dates & Times • jan1 = Date.new(2012, 1, 1) • dec31 = Date.new(2012, 1, 1) • (jan1..dec31).include?(Date.today) # => true • (jan1..dec31).include?(Date.today + 365) # => false

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REGULAR EXPRESSIONS

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REGULAR EXPRESSIONS Easy to Create • r = Regexp.new(“\d\d\d\d-\d\d-\d\d”) • r = /\d\d\d\d-\d\d-\d\d/

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REGULAR EXPRESSIONS Easy to Create • r = Regexp.new(“\d\d\d\d-\d\d-\d\d”) • r = /\d\d\d\d-\d\d-\d\d/ Match Strings • info = “Conference runs from 2012-06-04 to 2012-06-06” • Use =~ to find match location • info =~ /\d\d\d\d-\d\d-\d\d/ # => 21 • Use match to get the data back • info.match(/\d\d\d\d-\d\d-\d\d/) # => #

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REGULAR EXPRESSIONS Easy to Create • r = Regexp.new(“\d\d\d\d-\d\d-\d\d”) • r = /\d\d\d\d-\d\d-\d\d/ Match Strings • info = “Conference runs from 2012-06-04 to 2012-06-06” • Use =~ to find match location • info =~ /\d\d\d\d-\d\d-\d\d/ # => 21 • Use match to get the data back • info.match(/\d\d\d\d-\d\d-\d\d/) # => # Substitutions • info.sub(/\d\d\d\d-\d\d-\d\d/, “today”) - #=> “Conference runs from today to 2012-06-06” • info.gsub(/\d\d\d\d-\d\d-\d\d/, “today”) - #=> “Conference runs from today to today”

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REGULAR EXPRESSIONS Test with rubular.com

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CONDITIONALS AND LOOPS

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IF STATEMENTS if • if input == “quit” exit end

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IF STATEMENTS if • if input == “quit” exit end Single line if • exit if input == “quit”

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IF STATEMENTS if • if input == “quit” exit end Single line if • exit if input == “quit” unless • unless input == “quit” do_work end • do_work unless input == “quit”

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ELSE Test multiple conditions • if input == “quit” exit elsif input == “pause” sleep 20 else do_work end

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ELSE Test multiple conditions • if input == “quit” exit elsif input == “pause” sleep 20 else do_work end • Note the spelling of elsif

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CASE Ruby’s powerful case statement • case input when “quit” exit when “pause” sleep 20 when String puts “The input is #{input}” when 5..10 puts “The input was between 5 and 10” when /\d\d\d\d-\d\d-\d\d/ puts “The input looks like a date” else puts “I don’t understand you.” end

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WHILE Simple while loop • count = 0 • while count < 10 • puts count • count += 1 • end

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WHILE Simple while loop • count = 0 • while count < 10 • puts count • count += 1 • end += • Equivalent to count = count + 1 • Can be used with any number • And all basic math operations (*=, -=, etc.)

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WHILE Simple while loop • count = 0 • while count < 10 • puts count • count += 1 • end += • Equivalent to count = count + 1 • Can be used with any number • And all basic math operations (*=, -=, etc.) Inline while • count = 0 • puts count += 1 while count < 10

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UNLESS Unless is the inverted while • count = 0 • unless count >= 10 • puts count • count += 1 • end

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UNTIL until is the inverted while • count = 0 • until count >= 10 • puts count • count += 1 • end Inline until • count = 0 • puts count += 1 until count >= 10

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FOR For exists in Ruby • for fruit in fruits • puts “I love #{fruit} • end

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FOR For exists in Ruby • for fruit in fruits • puts “I love #{fruit} • end But we don’t use it.

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ITERATION THE RUBY WAY

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EACH Use each for iterating • fruits.each do |fruit| • puts “I love #{fruit}” • end

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EACH Use each for iterating • fruits.each do |fruit| • puts “I love #{fruit}” • end Use do & end for multi-line, {} for single-line • fruits.each {|fruit| puts “I love #{fruit}” }

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EACH Use each for iterating • fruits.each do |fruit| • puts “I love #{fruit}” • end Use do & end for multi-line, {} for single-line • fruits.each {|fruit| puts “I love #{fruit}” } Same syntax works for other forms of iterating • .map • .each_with_index • .each_key

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OBJECTS

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OBJECTS Objects • class Person end

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OBJECTS Objects • class Person end Inheritance • class Programmer < Person end

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OBJECTS Objects • class Person end Inheritance • class Programmer < Person end Constructors • class Person def initialize(name) @name = name end end

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RUBY ON RAILS

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RUBY ON RAILS What is Rails • Web Framework • Convention over Configuration • Geared toward database-backed web applications • Great for producing APIS

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EXAMPLE RAILS APP Demo time! • rails new demo • cd demo • rails generate scaffold person name:string age:integer • rails server

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USING JSON

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PARSING JSON In Rails • JSON.parse(json) Rhodes • Rho::JSON.parse(json)

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PARSING JSON In Rails • JSON.parse(json) Rhodes • Rho::JSON.parse(json) Both turn JSON into a Hash • { "name": "Bob", "age": 20, "friends": ["Alice", "Carol", "Dave"] } • { "name" => "Bob", "age" => 20, "friends" => ["Alice", "Carol", "Dave"] }

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XML IN RUBY XML is as easy as JSON • REXML::Document.new(xml_file)

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IRB INTERACTIVE RUBY

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IRB Command-line Ruby • irb • rails console

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IRB Command-line Ruby • irb • rails console Inspect data • puts x • x.inspect

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DEBUGGING Ruby Debugger • debugger gem, or ruby-debug • Both work similar to gdb

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DEBUGGING Read the Errors • They tell you line numbers NameError: undefined local variable or method `my_method' for # from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/ activerecord-3.2.2/lib/active_record/dynamic_matchers.rb:50:in `method_missing' from /Users/daniel/Projects/my_project/app/models/sign.rb:16:in `import' from (irb):4 from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@project/gems/railties-3.2.2/lib/ rails/commands/console.rb:47:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/ rails/commands/console.rb:8:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/ rails/commands.rb:41:in `' from script/rails:6:in `require' from script/rails:6:in `'

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DEBUGGING Read the Errors • They tell you line numbers NameError: undefined local variable or method `my_method' for # from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/ activerecord-3.2.2/lib/active_record/dynamic_matchers.rb:50:in `method_missing' from /Users/daniel/Projects/my_project/app/models/sign.rb:16:in `import' from (irb):4 from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@project/gems/railties-3.2.2/lib/ rails/commands/console.rb:47:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/ rails/commands/console.rb:8:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/ rails/commands.rb:41:in `' from script/rails:6:in `require' from script/rails:6:in `'

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DEBUGGING Read the Errors • They tell you line numbers NameError: undefined local variable or method `my_method' for # from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/ activerecord-3.2.2/lib/active_record/dynamic_matchers.rb:50:in `method_missing' from /Users/daniel/Projects/my_project/app/models/sign.rb:16:in `import' from (irb):4 from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@project/gems/railties-3.2.2/lib/ rails/commands/console.rb:47:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/ rails/commands/console.rb:8:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/ rails/commands.rb:41:in `' from script/rails:6:in `require' from script/rails:6:in `'

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DEBUGGING Read the Errors • They sometimes confuse you

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DEBUGGING Read the Errors • They sometimes confuse you @user.first_name

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DEBUGGING Read the Errors • They sometimes confuse you @user.first_name NoMethodError: undefined method `first_name' for nil:NilClass from (irb):1 from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/ lib/rails/commands/console.rb:47:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/ lib/rails/commands/console.rb:8:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/ lib/rails/commands.rb:41:in `' from script/rails:6:in `require' from script/rails:6:in `'

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DEBUGGING Read the Errors • They sometimes confuse you @user.first_name NoMethodError: undefined method `first_name' for nil:NilClass from (irb):1 from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/ lib/rails/commands/console.rb:47:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/ lib/rails/commands/console.rb:8:in `start' from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/ lib/rails/commands.rb:41:in `' from script/rails:6:in `require' from script/rails:6:in `'

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LEARN MORE

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LEARN MORE Documentation • http://ruby-doc.org • http://api.rubyonrails.org TryRuby • http://tryruby.org This Presentation • https://speakerdeck.com/u/danielmorrison • or shorter URL: http://bit.ly/LqCinu Talk to Me • @danielmorrison • http://collectiveidea.com

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