Ruby ALL the Closures - Speaker Deck

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Ruby ALL the closures Blocks, Procs and lambdas in ruby Tuesday, May 14, 13

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HOLA! • Pablo Astigarraga || PoTe • @poteland • github.com/pote Tuesday, May 14, 13

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Tuesday, May 14, 13

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Blocks, Procs and Lambdas Tuesday, May 14, 13

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Closures Tuesday, May 14, 13

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Tuesday, May 14, 13

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Closures Tuesday, May 14, 13

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Wikipedia A closure is a function or reference to a function together with a referencing environment - a table storing a reference to each of the non-local variables (also called free variables) of that function. A closure - unlike a plain function pointer - allows a function to access those non-local variables even when invoked outside of its immediate lexical scope. Tuesday, May 14, 13

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Closures def counter(): x = 0 def increment(y): nonlocal x x += y print(x) return increment Tuesday, May 14, 13

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Closures counter1_increment = counter() counter2_increment = counter() counter1_increment(1) # prints 1 counter1_increment(7) # prints 8 counter2_increment(1) # prints 1 counter1_increment(1) # prints 9 Tuesday, May 14, 13

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Closures def pretty_method pretty_variable = 0 this_is_a_lambda = ->(argument) { pretty_variable += argument puts pretty_variable } this_is_a_lambda end Tuesday, May 14, 13

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Closures method_1 = pretty_method method_2 = pretty_method method_1.call(1) # => 1 method_1.call(7) # => 8 method_2.call(1) # => 1 method_1.call(1) # => 9 Tuesday, May 14, 13

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Blocks Tuesday, May 14, 13

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Blocks 5.times do puts 'Una más y no jodemos más!' end Tuesday, May 14, 13

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blocks 999.times do |index| puts "#{ index } elefantes se balanceaban sobre la tela de una araña, como veian que resistía fueron a buscar otro elefante" end Tuesday, May 14, 13

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Blocks ['python', 'ruby', 'lua'].each do |language| puts "#{ language } is a pretty cool language!" end #=> python is a pretty cool language! # ruby is a pretty cool language! # lua is a pretty cool language! Tuesday, May 14, 13

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Blocks 5.times do |index| puts 'Lalala' end 5.times { |index| puts 'Lalala' } 5.times { |index| puts 'Lalala' } Tuesday, May 14, 13

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Blocks Blocks are chunks of code that are used by a method. Tuesday, May 14, 13

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How? Tuesday, May 14, 13

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Let’s make our own Tuesday, May 14, 13

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Procedures A.K.A “Procs” Tuesday, May 14, 13

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Procs p = Proc.new do |text| text.split(' ').each do |word| puts "#{ word } \n" } end puts "- ♪ 㽈" end p.call("uno dos tres cuatro cinco cinco seis") Tuesday, May 14, 13

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Procs p = Proc.new do |text| text.split(' ').each do |word| puts "#{ word } \n" } end puts "- ♪ 㽈" end p.call("uno dos tres cuatro cinco cinco seis") Tuesday, May 14, 13

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p = Proc.new do | text| text.split(' ').each do |word| puts "#{ word } \n" } end Tuesday, May 14, 13

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p = Proc.new do |text| text.split(' Tuesday, May 14, 13

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Procs are objects Tuesday, May 14, 13

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blocks == Procs Tuesday, May 14, 13

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Who has done this? (function () { $.ajax({ url: "json.txt", dataType: 'json', cache: false, success: function (data, textStatus, jqXHR) { if (data.mySuccessProperty == "succeeded") { doX(); (function () { eval(data.dynamicFunction)(); })(); } else { doY(); (function () { alert("Z"); })(); } }, error: function (jqXHR, textStatus, error) { // handle error alert("error" + error); } }); })(); Tuesday, May 14, 13

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Procs callbacks = { success: Proc.new { |result| Services::EverythingWentWell.call(result: result) Services::NotifyEveryone.call }, error: Proc.new { |result| # Clean up mess # Log problem # Dance Polka } } def method_that_does_things(callbacks) if do_things callbacks[:success].call(result_of_things) else callbacks[:error].call(result_of_things) end end Tuesday, May 14, 13

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Procs def persist!(hooks) hooks[:before_validate].call hooks[:before_save].call save hooks[:after_save].call end Tuesday, May 14, 13

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Lambdas Tuesday, May 14, 13

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Lambdas class Array def iterate!(code) self.each_with_index do |n, i| self[i] = code.call(n) end end end array = [1, 2, 3, 4] array.iterate!(lambda { |n| n ** 2 }) puts array.inspect # => [1, 4, 9, 16] Tuesday, May 14, 13

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Lambdas def args(code) one, two = 1, 2 code.call(one, two) end args(Proc.new{|a, b, c| puts "Give me a #{a} and a #{b} and a #{c.class}"}) args(lambda{|a, b, c| puts "Give me a #{a} and a #{b} and a #{c.class}"}) # => Give me a 1 and a 2 and a NilClass # *.rb:8: ArgumentError: wrong number of arguments (2 for 3) (ArgumentError) Tuesday, May 14, 13

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Lambdas def proc_return Proc.new { return "Proc.new"}.call return "proc_return method finished" end def lambda_return lambda { return "lambda" }.call return "lambda_return method finished" end puts proc_return puts lambda_return # => Proc.new # => lambda_return method finished Tuesday, May 14, 13

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Questions? Tuesday, May 14, 13

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Gracias! @poteland Tuesday, May 14, 13

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Links @poteland * Understanding Ruby Blocks, Procs and Lambdas - http://bit.ly/9qcstJ * This Talk - http://bit.ly/18IFJmP * More info - http://bit.ly/r8BnTA Tuesday, May 14, 13