Ruby ALL the Closures

I was asked to give an introductory talk about blocks, Procs and Lambdas in the local Ruby Meetup in Montevideo. This is the result.

Transcript

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

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

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4. Blocks, Procs and
   Lambdas
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5. Closures
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6. Tuesday, May 14, 13
   

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7. Closures
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8. 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.
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9. Closures
   def counter():
   x = 0
   def increment(y):
   nonlocal x
   x += y
   print(x)
   return increment
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10. 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
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11. Closures
    def pretty_method
    pretty_variable = 0
    this_is_a_lambda = ->(argument) {
    pretty_variable += argument
    puts pretty_variable
    }
    this_is_a_lambda
    end
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12. 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
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13. Blocks
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14. Blocks
    5.times do
    puts 'Una más y no jodemos más!'
    end
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15. 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
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16. 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!
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17. Blocks
    5.times do |index|
    puts 'Lalala'
    end
    5.times { |index|
    puts 'Lalala'
    }
    5.times { |index| puts 'Lalala' }
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18. Blocks
    Blocks are chunks of code that are used
    by a method.
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19. How?
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20. Let’s make our own
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21. 
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22. Procedures
    A.K.A “Procs”
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23. 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")
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24. 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")
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25. p = Proc.new do |
    text|
    text.split('
    ').each do |word|
    puts "#{ word }
    \n" }
    end
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26. p = Proc.new
    do |text|
    text.split('
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27. Procs
    are
    objects
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28. 
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29. blocks == Procs
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30. 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);
    }
    });
    })();
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31. 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);
    }
    });
    })();
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32. 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
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33. Procs
    def persist!(hooks)
    hooks[:before_validate].call
    hooks[:before_save].call
    save
    hooks[:after_save].call
    end
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34. Lambdas
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35. 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]
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36. 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)
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37. 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
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38. Questions?
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39. Gracias!
    @poteland
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40. Links
    @poteland
    * Understanding Ruby Blocks, Procs
    and Lambdas - http://bit.ly/9qcstJ
    * This Talk - http://bit.ly/18IFJmP
    * More info - http://bit.ly/r8BnTA
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