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This was the second speech of a three day Rails training I gave in Tulsa, OK in the spring 2010.

This was the second speech of a three day Rails training I gave in Tulsa, OK in the spring 2010.

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Ruby Ruby Presentation Transcript

  • Ruby The programming language that made Rails possible
  • The Oath
  • The Oath “I do solemnly swear: I will not consider this an exhaustive Ruby lesson and I will study Ruby more as I progress in Rails, so James will not come take my keyboard away!”
  • irb The secret weapon of the Rubyists
  • The REPL
  • The REPL Ruby comes with a Read-Eval-Print-Loop tool called irb
  • The REPL Ruby comes with a Read-Eval-Print-Loop tool called irb In short, you feed it some Ruby and it prints results
  • The REPL Ruby comes with a Read-Eval-Print-Loop tool called irb In short, you feed it some Ruby and it prints results This is an excellent way to learn the language
  • The REPL Ruby comes with a Read-Eval-Print-Loop tool called irb In short, you feed it some Ruby and it prints results This is an excellent way to learn the language It becomes a powerful data management tool when used with Rails
  • The REPL Ruby comes with a Read-Eval-Print-Loop tool called irb In short, you feed it some Ruby and it prints results This is an excellent way to learn the language It becomes a powerful data management tool when used with Rails Do yourself a favor and start playing with irb a lot
  • Using irb
  • Using irb $ irb >> 1 + 2 => 3 >> "james".capitalize => "James" >> %w[y b u R].reverse => ["R", "u", "b", "y"] >> _.join("-") => "R-u-b-y" >> exit
  • Using irb Run irb to launch it $ irb >> 1 + 2 => 3 >> "james".capitalize => "James" >> %w[y b u R].reverse => ["R", "u", "b", "y"] >> _.join("-") => "R-u-b-y" >> exit
  • Using irb Run irb to launch it $ irb You enter Ruby >> 1 + 2 expressions => 3 >> "james".capitalize => "James" >> %w[y b u R].reverse => ["R", "u", "b", "y"] >> _.join("-") => "R-u-b-y" >> exit
  • Using irb Run irb to launch it $ irb You enter Ruby >> 1 + 2 expressions => 3 >> "james".capitalize => "James" irb responds with the >> %w[y b u R].reverse results as you type => ["R", "u", "b", "y"] >> _.join("-") => "R-u-b-y" >> exit
  • Using irb Run irb to launch it $ irb You enter Ruby >> 1 + 2 expressions => 3 >> "james".capitalize => "James" irb responds with the >> %w[y b u R].reverse results as you type => ["R", "u", "b", "y"] >> _.join("-") => "R-u-b-y" _ holds the last result >> exit
  • Using irb Run irb to launch it $ irb You enter Ruby >> 1 + 2 expressions => 3 >> "james".capitalize => "James" irb responds with the >> %w[y b u R].reverse results as you type => ["R", "u", "b", "y"] >> _.join("-") => "R-u-b-y" _ holds the last result >> exit Use exit() to quit
  • Data Types The building blocks of Ruby
  • Data Types and Structures
  • Data Types and Structures Ruby has data types common to most programming languages: String, Integer, Float, …
  • Data Types and Structures Ruby has data types common to most programming languages: String, Integer, Float, … Ruby has two primary data structures: Array and Hash
  • Data Types and Structures Ruby has data types common to most programming languages: String, Integer, Float, … Ruby has two primary data structures: Array and Hash These structures are very versatile and can serve as sets, queues, stacks, …
  • Data Types and Structures Ruby has data types common to most programming languages: String, Integer, Float, … Ruby has two primary data structures: Array and Hash These structures are very versatile and can serve as sets, queues, stacks, … Ruby has some other data types, like Time
  • Data Types and Structures Ruby has data types common to most programming languages: String, Integer, Float, … Ruby has two primary data structures: Array and Hash These structures are very versatile and can serve as sets, queues, stacks, … Ruby has some other data types, like Time All of the above are full objects in Ruby
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • String “ta lot of escapesn#{1 + 2}” ‘less ( or ’)’ 255 0377 Integer 0xFF 0b11111111 0.00003 Float 3.0e-5 [“James”, “Edward”, “Gray”, “II”] Array %w[James Edward Gray II] Hash {“name” => “James”, “age” => 33} Symbol :first_name Regexp /AJ(?:ames )?E(?:dward )?G(?:ray )?(?:II|2)z/ Time.now Time Time.local(2010, 3, 10) Time.utc(2010, 3, 10)
  • Working With Strings
  • Working With Strings >> space = "textra space n" => "textra space n" >> space.strip => "extra space" >> space.rstrip => "textra space" >> "James".delete("aeiou") => "Jms" >> date = "March 2010" => "March 2010" >> date[0..4] => "March" >> date[-2..-1] => "10" >> date[/d+/] => "2010"
  • Working With Strings >> space = "textra space n" String provides: => >> "textra space n" space.strip => "extra space" >> space.rstrip => "textra space" >> "James".delete("aeiou") => "Jms" >> date = "March 2010" => "March 2010" >> date[0..4] => "March" >> date[-2..-1] => "10" >> date[/d+/] => "2010"
  • Working With Strings >> space = "textra space n" String provides: => >> "textra space n" space.strip => "extra space" Case changing >> => space.rstrip "textra space" >> "James".delete("aeiou") => "Jms" >> date = "March 2010" => "March 2010" >> date[0..4] => "March" >> date[-2..-1] => "10" >> date[/d+/] => "2010"
  • Working With Strings >> space = "textra space n" String provides: => >> "textra space n" space.strip => "extra space" Case changing >> => space.rstrip "textra space" Whitespace stripping >> "James".delete("aeiou") => "Jms" >> date = "March 2010" => "March 2010" >> date[0..4] => "March" >> date[-2..-1] => "10" >> date[/d+/] => "2010"
  • Working With Strings >> space = "textra space n" String provides: => >> "textra space n" space.strip => "extra space" Case changing >> => space.rstrip "textra space" Whitespace stripping >> "James".delete("aeiou") => "Jms" General editing >> => date = "March 2010" "March 2010" >> date[0..4] => "March" >> date[-2..-1] => "10" >> date[/d+/] => "2010"
  • Working With Strings >> space = "textra space n" String provides: => >> "textra space n" space.strip => "extra space" Case changing >> => space.rstrip "textra space" Whitespace stripping >> "James".delete("aeiou") => "Jms" General editing >> => date = "March 2010" "March 2010" >> date[0..4] Indexing => "March" >> date[-2..-1] => "10" >> date[/d+/] => "2010"
  • Working With Strings >> space = "textra space n" String provides: => >> "textra space n" space.strip => "extra space" Case changing >> => space.rstrip "textra space" Whitespace stripping >> "James".delete("aeiou") => "Jms" General editing >> => date = "March 2010" "March 2010" >> date[0..4] Indexing => "March" >> date[-2..-1] => "10" … >> date[/d+/] => "2010"
  • Working With Arrays
  • Working With Arrays >> a = [0, 1] => [0, 1] >> a << 2 << 3 << 4 => [0, 1, 2, 3, 4] >> a.pop => 4 >> a => [0, 1, 2, 3] >> a[1] => 1 >> a[1..-1] => [1, 2, 3] >> a & [0, 2, 4, 6] => [0, 2] >> a | [42] => [0, 1, 2, 3, 42]
  • Working With Arrays >> a = [0, 1] Array provides: => >> [0, 1] a << 2 << 3 << 4 => [0, 1, 2, 3, 4] >> a.pop => 4 >> a => [0, 1, 2, 3] >> a[1] => 1 >> a[1..-1] => [1, 2, 3] >> a & [0, 2, 4, 6] => [0, 2] >> a | [42] => [0, 1, 2, 3, 42]
  • Working With Arrays >> a = [0, 1] Array provides: => >> [0, 1] a << 2 << 3 << 4 => [0, 1, 2, 3, 4] Adding elements >> => a.pop 4 >> a => [0, 1, 2, 3] >> a[1] => 1 >> a[1..-1] => [1, 2, 3] >> a & [0, 2, 4, 6] => [0, 2] >> a | [42] => [0, 1, 2, 3, 42]
  • Working With Arrays >> a = [0, 1] Array provides: => >> [0, 1] a << 2 << 3 << 4 => [0, 1, 2, 3, 4] Adding elements >> => a.pop 4 >> a Removing elements => [0, 1, 2, 3] >> a[1] => 1 >> a[1..-1] => [1, 2, 3] >> a & [0, 2, 4, 6] => [0, 2] >> a | [42] => [0, 1, 2, 3, 42]
  • Working With Arrays >> a = [0, 1] Array provides: => >> [0, 1] a << 2 << 3 << 4 => [0, 1, 2, 3, 4] Adding elements >> => a.pop 4 >> a Removing elements => [0, 1, 2, 3] >> a[1] Indexing => >> 1 a[1..-1] => [1, 2, 3] >> a & [0, 2, 4, 6] => [0, 2] >> a | [42] => [0, 1, 2, 3, 42]
  • Working With Arrays >> a = [0, 1] Array provides: => >> [0, 1] a << 2 << 3 << 4 => [0, 1, 2, 3, 4] Adding elements >> => a.pop 4 >> a Removing elements => [0, 1, 2, 3] >> a[1] Indexing => >> 1 a[1..-1] => [1, 2, 3] Set operations >> a & [0, 2, 4, 6] => [0, 2] >> a | [42] => [0, 1, 2, 3, 42]
  • Working With Arrays >> a = [0, 1] Array provides: => >> [0, 1] a << 2 << 3 << 4 => [0, 1, 2, 3, 4] Adding elements >> => a.pop 4 >> a Removing elements => [0, 1, 2, 3] >> a[1] Indexing => >> 1 a[1..-1] => [1, 2, 3] Set operations >> a & [0, 2, 4, 6] => [0, 2] … >> a | [42] => [0, 1, 2, 3, 42]
  • Working With Hashes
  • Working With Hashes >> h = {:a => 1, :b => 2} => {:a=>1, :b=>2} >> h[:b] => 2 >> h[:c] = 3 => 3 >> h => {:a=>1, :b=>2, :c=>3} >> h.keys => [:a, :b, :c] >> h.values => [1, 2, 3] >> h.include? :c => true >> h.include? :d => false
  • Working With Hashes >> h = {:a => 1, :b => 2} Hash provides: => >> {:a=>1, :b=>2} h[:b] => 2 >> h[:c] = 3 => 3 >> h => {:a=>1, :b=>2, :c=>3} >> h.keys => [:a, :b, :c] >> h.values => [1, 2, 3] >> h.include? :c => true >> h.include? :d => false
  • Working With Hashes >> h = {:a => 1, :b => 2} Hash provides: => >> {:a=>1, :b=>2} h[:b] => 2 Key-value storage >> => h[:c] = 3 3 >> h => {:a=>1, :b=>2, :c=>3} >> h.keys => [:a, :b, :c] >> h.values => [1, 2, 3] >> h.include? :c => true >> h.include? :d => false
  • Working With Hashes >> h = {:a => 1, :b => 2} Hash provides: => >> {:a=>1, :b=>2} h[:b] => 2 Key-value storage >> => h[:c] = 3 3 >> h Key addition/removal => {:a=>1, :b=>2, :c=>3} >> h.keys => [:a, :b, :c] >> h.values => [1, 2, 3] >> h.include? :c => true >> h.include? :d => false
  • Working With Hashes >> h = {:a => 1, :b => 2} Hash provides: => >> {:a=>1, :b=>2} h[:b] => 2 Key-value storage >> => h[:c] = 3 3 >> h Key addition/removal => {:a=>1, :b=>2, :c=>3} >> h.keys Indexing => >> [:a, :b, :c] h.values => [1, 2, 3] >> h.include? :c => true >> h.include? :d => false
  • Working With Hashes >> h = {:a => 1, :b => 2} Hash provides: => >> {:a=>1, :b=>2} h[:b] => 2 Key-value storage >> => h[:c] = 3 3 >> h Key addition/removal => {:a=>1, :b=>2, :c=>3} >> h.keys Indexing => >> [:a, :b, :c] h.values => [1, 2, 3] Queries >> h.include? :c => true >> h.include? :d => false
  • Working With Hashes >> h = {:a => 1, :b => 2} Hash provides: => >> {:a=>1, :b=>2} h[:b] => 2 Key-value storage >> => h[:c] = 3 3 >> h Key addition/removal => {:a=>1, :b=>2, :c=>3} >> h.keys Indexing => >> [:a, :b, :c] h.values => [1, 2, 3] Queries >> h.include? :c => true … >> h.include? :d => false
  • Type Conversions
  • Type Conversions >> pi = "3.1415" => "3.1415" >> pi.to_f => 3.1415 >> pi.to_i => 3 >> num = 42 => 42 >> num.to_s => "42" >> num.to_s(16) => "2a" >> animals = "chickens,cows,Rubyists" => "chickens,cows,Rubyists" >> animals.split(",") => ["chickens", "cows", "Rubyists"] >> animals.split(",", 2) => ["chickens", "cows,Rubyists"] >> animals.split(",").join(" | ") => "chickens | cows | Rubyists"
  • Type Conversions Ruby has many >> pi = "3.1415" => "3.1415" conversion methods >> pi.to_f => 3.1415 >> pi.to_i => 3 >> num = 42 => 42 >> num.to_s => "42" >> num.to_s(16) => "2a" >> animals = "chickens,cows,Rubyists" => "chickens,cows,Rubyists" >> animals.split(",") => ["chickens", "cows", "Rubyists"] >> animals.split(",", 2) => ["chickens", "cows,Rubyists"] >> animals.split(",").join(" | ") => "chickens | cows | Rubyists"
  • Type Conversions Ruby has many >> pi = "3.1415" => "3.1415" conversion methods >> pi.to_f => 3.1415 >> pi.to_i Strings can become => 3 Integers or Floats >> => num = 42 42 >> num.to_s => "42" >> num.to_s(16) => "2a" >> animals = "chickens,cows,Rubyists" => "chickens,cows,Rubyists" >> animals.split(",") => ["chickens", "cows", "Rubyists"] >> animals.split(",", 2) => ["chickens", "cows,Rubyists"] >> animals.split(",").join(" | ") => "chickens | cows | Rubyists"
  • Type Conversions Ruby has many >> pi = "3.1415" => "3.1415" conversion methods >> pi.to_f => 3.1415 >> pi.to_i Strings can become => 3 Integers or Floats >> => num = 42 42 >> num.to_s => "42" Numbers can >> num.to_s(16) => "2a" Stringified in a base >> animals = "chickens,cows,Rubyists" => "chickens,cows,Rubyists" >> animals.split(",") => ["chickens", "cows", "Rubyists"] >> animals.split(",", 2) => ["chickens", "cows,Rubyists"] >> animals.split(",").join(" | ") => "chickens | cows | Rubyists"
  • Type Conversions Ruby has many >> pi = "3.1415" => "3.1415" conversion methods >> pi.to_f => 3.1415 >> pi.to_i Strings can become => 3 Integers or Floats >> => num = 42 42 >> num.to_s => "42" Numbers can >> num.to_s(16) => "2a" Stringified in a base >> animals = "chickens,cows,Rubyists" => "chickens,cows,Rubyists" Strings become >> => animals.split(",") ["chickens", "cows", "Rubyists"] Arrays, and go back >> => animals.split(",", 2) ["chickens", "cows,Rubyists"] >> animals.split(",").join(" | ") => "chickens | cows | Rubyists"
  • Type Conversions Ruby has many >> pi = "3.1415" => "3.1415" conversion methods >> pi.to_f => 3.1415 >> pi.to_i Strings can become => 3 Integers or Floats >> => num = 42 42 >> num.to_s => "42" Numbers can >> num.to_s(16) => "2a" Stringified in a base >> animals = "chickens,cows,Rubyists" => "chickens,cows,Rubyists" Strings become >> => animals.split(",") ["chickens", "cows", "Rubyists"] Arrays, and go back >> => animals.split(",", 2) ["chickens", "cows,Rubyists"] >> animals.split(",").join(" | ") => "chickens | cows | Rubyists" …
  • Flow Control Conditional logic
  • The if statement
  • The if statement num = rand(10) print "#{num}: " if num == 7 puts "Lucky!" elsif num <= 3 puts "A little low." else puts "A boring number." end # >> 2: A little low.
  • The if statement Ruby has if/elsif/else conditionals num = rand(10) print "#{num}: " if num == 7 puts "Lucky!" elsif num <= 3 puts "A little low." else puts "A boring number." end # >> 2: A little low.
  • The if statement Ruby has if/elsif/else conditionals num = rand(10) print "#{num}: " The code is run if the if num == 7 puts "Lucky!" condition is true elsif num <= 3 puts "A little low." else puts "A boring number." end # >> 2: A little low.
  • The if statement Ruby has if/elsif/else conditionals num = rand(10) print "#{num}: " The code is run if the if num == 7 puts "Lucky!" condition is true elsif num <= 3 puts "A little low." In Ruby, false and nil else puts "A boring number." are false and all other end # >> 2: A little low. objects are true (0, “”, etc.)
  • The if statement Ruby has if/elsif/else conditionals num = rand(10) print "#{num}: " The code is run if the if num == 7 puts "Lucky!" condition is true elsif num <= 3 puts "A little low." In Ruby, false and nil else puts "A boring number." are false and all other end # >> 2: A little low. objects are true (0, “”, etc.)
  • When Things go Wrong
  • When Things go Wrong >> 42 / 0 ZeroDivisionError: divided by 0 from (irb):1:in `/' from (irb):1 from :0
  • When Things go Wrong Ruby “raises” errors (called Exceptions) when things go wrong >> 42 / 0 ZeroDivisionError: divided by 0 from (irb):1:in `/' from (irb):1 from :0
  • When Things go Wrong Ruby “raises” errors (called Exceptions) when things go wrong Error objects have a >> 42 / 0 ZeroDivisionError: divided by 0 type, message, and from (irb):1:in `/' from (irb):1 backtrace from :0
  • When Things go Wrong Ruby “raises” errors (called Exceptions) when things go wrong Error objects have a >> 42 / 0 ZeroDivisionError: divided by 0 type, message, and from (irb):1:in `/' from (irb):1 backtrace from :0
  • When Things go Wrong Ruby “raises” errors (called Exceptions) when things go wrong Error objects have a >> 42 / 0 ZeroDivisionError: divided by 0 type, message, and from (irb):1:in `/' from (irb):1 backtrace from :0
  • When Things go Wrong Ruby “raises” errors (called Exceptions) when things go wrong Error objects have a >> 42 / 0 ZeroDivisionError: divided by 0 type, message, and from (irb):1:in `/' from (irb):1 backtrace from :0 By default, processing stops if the error isn’t “rescued”
  • Exception Handling
  • Exception Handling >> begin >> n = 42 / 0 >> rescue ZeroDivisionError => error >> n=0 >> end => 0 >> n => 0
  • Exception Handling Put code that might raise errors between >> begin >> n = 42 / 0 begin … end >> >> rescue ZeroDivisionError => error n=0 >> end => 0 >> n => 0
  • Exception Handling Put code that might raise errors between >> begin >> n = 42 / 0 begin … end >> >> rescue ZeroDivisionError => error n=0 >> end Add rescue clauses => >> 0 n for the error types you => 0 want to handle
  • Objects and Methods In Ruby, very nearly everything is an object
  • Everything is an Object
  • Everything is an Object >> -42.abs => 42 >> 3.times { puts "Howdy" } Howdy Howdy Howdy => 3
  • Everything is an Object With a few very minor exceptions, everything >> -42.abs => 42 in Ruby is an Object >> 3.times { puts "Howdy" } Howdy Howdy Howdy => 3
  • Everything is an Object With a few very minor exceptions, everything >> -42.abs => 42 in Ruby is an Object >> 3.times { puts "Howdy" } Howdy Howdy Even a number literal is Howdy an Object and you can => 3 call methods on it
  • Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end def first=(first) @first = first end def first @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end def first=(first) @first = first end def first @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end def first=(first) @first = first end def first @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end def first=(first) @first = first end def first @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end def first=(first) @first = first end def first @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end def first=(first) @first = first end def first @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end dana = Name.new("Dana") james = Name.new def first=(first) james.first = "James" @first = first puts dana.first end puts james.first # >> Dana def first # >> James @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end dana = Name.new("Dana") james = Name.new def first=(first) james.first = "James" @first = first puts dana.first end puts james.first # >> Dana def first # >> James @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end dana = Name.new("Dana") james = Name.new def first=(first) james.first = "James" @first = first puts dana.first end puts james.first # >> Dana def first # >> James @first end end Instance Variables Private, per object storage
  • class Name def initialize(first = nil) self.first = first end dana = Name.new("Dana") james = Name.new def first=(first) james.first = "James" @first = first puts dana.first end puts james.first # >> Dana def first # >> James @first end end Instance Variables Private, per object storage
  • Single Inheritance
  • Single Inheritance class Parent def greet @greeting ||= "Hello!" end end class Child < Parent def initialize @greeting = "Yo!" end end puts Parent.new.greet puts Child.new.greet # >> Hello! # >> Yo!
  • Single Inheritance A Class can declare class Parent def greet one parent @greeting ||= "Hello!" end end class Child < Parent def initialize @greeting = "Yo!" end end puts Parent.new.greet puts Child.new.greet # >> Hello! # >> Yo!
  • Single Inheritance A Class can declare class Parent def greet one parent @greeting ||= "Hello!" end A child inherits all end class Child < Parent behavior from all def initialize @greeting = "Yo!" ancestors end end puts Parent.new.greet puts Child.new.greet # >> Hello! # >> Yo!
  • Single Inheritance A Class can declare class Parent def greet one parent @greeting ||= "Hello!" end A child inherits all end class Child < Parent behavior from all def initialize @greeting = "Yo!" ancestors end end Ruby’s Object is the puts Parent.new.greet puts Child.new.greet highest parent for all # >> Hello! Classes # >> Yo!
  • Questions and Dangerous Methods
  • Questions and Dangerous Methods >> 0.zero? => true >> 0.0.zero? => true >> 0.00001.zero? => false >> s = "string" => "string" >> s.upcase => "STRING" >> s => "string" >> s.upcase! => "STRING" >> s => "STRING"
  • Questions and Dangerous Methods Ruby has some >> => 0.zero? true method name >> => 0.0.zero? true conventions >> => 0.00001.zero? false >> s = "string" => "string" >> s.upcase => "STRING" >> s => "string" >> s.upcase! => "STRING" >> s => "STRING"
  • Questions and Dangerous Methods Ruby has some >> => 0.zero? true method name >> => 0.0.zero? true conventions >> => 0.00001.zero? false Question methods >> => s = "string" "string" (answering true or >> s.upcase => "STRING" false) end in ? >> s => "string" >> s.upcase! => "STRING" >> s => "STRING"
  • Questions and Dangerous Methods Ruby has some >> => 0.zero? true method name >> => 0.0.zero? true conventions >> => 0.00001.zero? false Question methods >> => s = "string" "string" (answering true or >> s.upcase => "STRING" false) end in ? >> s => "string" >> s.upcase! Dangerous methods => "STRING" >> s end in ! => "STRING"
  • “Mixins” A uniquely Ruby way to share methods
  • Modules
  • Modules module Netstring def to_netstring(*args) str = to_s(*args) "#{str.length}:#{str}," end end class String include Netstring end class Integer < Numeric include Netstring end p "James".to_netstring p 42.to_netstring(2) # >> "5:James," # >> "6:101010,"
  • Modules module Netstring def to_netstring(*args) Ruby doesn’t have str = to_s(*args) "#{str.length}:#{str}," multiple inheritance end end class String include Netstring end class Integer < Numeric include Netstring end p "James".to_netstring p 42.to_netstring(2) # >> "5:James," # >> "6:101010,"
  • Modules module Netstring def to_netstring(*args) Ruby doesn’t have str = to_s(*args) "#{str.length}:#{str}," multiple inheritance end end Instead, we can “mix” a class String include Netstring Module of methods end “in”to a Class class Integer < Numeric include Netstring end p "James".to_netstring p 42.to_netstring(2) # >> "5:James," # >> "6:101010,"
  • Modules module Netstring def to_netstring(*args) Ruby doesn’t have str = to_s(*args) "#{str.length}:#{str}," multiple inheritance end end Instead, we can “mix” a class String include Netstring Module of methods end “in”to a Class class Integer < Numeric include Netstring end We call these p "James".to_netstring Modules “mixins” p # 42.to_netstring(2) >> "5:James," # >> "6:101010,"
  • Modules module Netstring def to_netstring(*args) Ruby doesn’t have str = to_s(*args) "#{str.length}:#{str}," multiple inheritance end end Instead, we can “mix” a class String include Netstring Module of methods end “in”to a Class class Integer < Numeric include Netstring end We call these p "James".to_netstring Modules “mixins” p # 42.to_netstring(2) >> "5:James," # >> "6:101010,"
  • Blocks and Iterators Rubyists turn their noses up at loops
  • Blocks
  • Blocks def until_successful loop do break if yield == :success end end until_successful { puts "Called." :success if rand(3).zero? } # >> Called. # >> Called. # >> Called. # >> Called.
  • Blocks In Ruby, you can pass def until_successful a block (some code) to loop do break if yield == :success a called method end end until_successful { puts "Called." :success if rand(3).zero? } # >> Called. # >> Called. # >> Called. # >> Called.
  • Blocks In Ruby, you can pass def until_successful a block (some code) to loop do break if yield == :success a called method end end Block code is in until_successful { puts "Called." { … } or do … end :success if rand(3).zero? } # >> Called. # >> Called. # >> Called. # >> Called.
  • Blocks In Ruby, you can pass def until_successful a block (some code) to loop do break if yield == :success a called method end end Block code is in until_successful { puts "Called." { … } or do … end :success if rand(3).zero? } That method can run # >> Called. # >> Called. the passed code with # >> Called. # >> Called. yield
  • for (…; …; …) { }
  • for (…; …; …) { } Rubyists Don’t “Loop” We “iterate” instead
  • The each() Iterator
  • The each() Iterator name = %w[James Edward Gray II] name.each do |word| puts word.reverse end # >> semaJ # >> drawdE # >> yarG # >> II
  • The each() Iterator Let Ruby manage name = %w[James Edward Gray II] indexes for you name.each do |word| puts word.reverse end # >> semaJ # >> drawdE # >> yarG # >> II
  • The each() Iterator Let Ruby manage name = %w[James Edward Gray II] indexes for you name.each do |word| puts word.reverse end each() will call the # >> semaJ # >> drawdE block once with every # >> yarG # >> II item of the collection
  • The map() Iterator
  • The map() Iterator nums = *1..5 p nums p nums.map { |n| n ** 2 } # >> [1, 2, 3, 4, 5] # >> [1, 4, 9, 16, 25]
  • The map() Iterator map() is used to transform your collection nums = *1..5 p nums p nums.map { |n| n ** 2 } # >> [1, 2, 3, 4, 5] # >> [1, 4, 9, 16, 25]
  • The map() Iterator map() is used to transform your collection nums = *1..5 Each item of the p nums p nums.map { |n| n ** 2 } collection is passed # >> [1, 2, 3, 4, 5] into the block and the # >> [1, 4, 9, 16, 25] result of the block replaces that item in a new collection
  • The map() Iterator map() is used to transform your collection nums = *1..5 Each item of the p nums p nums.map { |n| n ** 2 } collection is passed # >> [1, 2, 3, 4, 5] into the block and the # >> [1, 4, 9, 16, 25] result of the block replaces that item in a new collection
  • The select() Iterator
  • The select() Iterator nums = *1..10 p nums p nums.select { |n| n % 2 == 0 } # >> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] # >> [2, 4, 6, 8, 10]
  • The select() Iterator select() can be used to filter a collection nums = *1..10 p nums p nums.select { |n| n % 2 == 0 } # >> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] # >> [2, 4, 6, 8, 10]
  • The select() Iterator select() can be used to filter a collection Each item is passed nums = *1..10 into the block and if the p nums p nums.select { |n| n % 2 == 0 } # >> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] block conditional # >> [2, 4, 6, 8, 10] evaluates to a true value the item is placed in the new collection
  • The select() Iterator select() can be used to filter a collection Each item is passed nums = *1..10 into the block and if the p nums p nums.select { |n| n % 2 == 0 } # >> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] block conditional # >> [2, 4, 6, 8, 10] evaluates to a true value the item is placed in the new collection
  • And Much, Much More! I have barely scratched the surface of Ruby
  • Ruby is a Rich Language
  • Ruby is a Rich Language Over 140 methods on String and over 70 on Array
  • Ruby is a Rich Language Over 140 methods on String and over 70 on Array Automatic “big math” conversions
  • Ruby is a Rich Language Over 140 methods on String and over 70 on Array Automatic “big math” conversions A very capable case statement (multi-branch conditional)
  • Ruby is a Rich Language Over 140 methods on String and over 70 on Array Automatic “big math” conversions A very capable case statement (multi-branch conditional) Custom per object behaviors
  • Ruby is a Rich Language Over 140 methods on String and over 70 on Array Automatic “big math” conversions A very capable case statement (multi-branch conditional) Custom per object behaviors Over 30 iterators
  • Ruby is a Rich Language Over 140 methods on String and over 70 on Array Automatic “big math” conversions A very capable case statement (multi-branch conditional) Custom per object behaviors Over 30 iterators Powerful reflection capabilities
  • Questions?
  • Learning Ruby from Ruby Lab Your book has instructions on how to use irb to learn more about Ruby from the language itself