Stupid Ruby Tricks

Learn some useful and sometimes hidden Ruby features.

Given at WNYRuby in December 2011. http://www.meetup.com/Western-New-York-Ruby/

Transcript

1. stupid ruby tricks
   and some useful ones
   Nick Quaranto @qrush
   

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2. stupid ruby tricks
   and some useful ones
   Nick Quaranto @qrush
   1/23 - 5%
   

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3. ruby -c: Syntax checking
   $ echo "class Foo" | ruby -c
   -:1: syntax error, unexpected $end
   $ echo "class Foo; end" | ruby -c
   Syntax OK
   2/23 - 9%
   

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4. ruby -w: Indent checking (1.9+)
   $ cat bad.rb
   class Foo
   def bar
   if false
   puts "LOL"
   end
   end
   $ ruby -w bad.rb
   bad.rb:5: warning: mismatched indentations at 'end' with 'if'
   bad.rb:6: warning: mismatched indentations at 'end' with 'def
   bad.rb:6: syntax error, unexpected $end, expecting keyword_en
   3/23 - 14%
   

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5. ruby -p, -e, -i
   $ echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
   MATZ
   $ echo matz > /tmp/junk
   $ cat /tmp/junk
   matz
   $ ruby -p -i.bak -e '$_.upcase!' /tmp/junk
   $ cat /tmp/junk
   MATZ
   $ cat /tmp/junk.bak
   matz
   4/23 - 18%
   

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6. underscores in numbers
   1_000.times do
   puts "ROFL!"
   end
   (1..300_000_000).each do |n|
   puts "LMAO!"
   end
   5/23 - 22%
   

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7. underscore in irb
   # %w(a b c).map(&:succ)
   ["b", "c", "d"]
   # _
   ["b", "c", "d"]
   # letters = _
   ["b", "c", "d"]
   6/23 - 27%
   

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8. string concatenation
   # "ab" + "cd"
   "abcd"
   # "ab" "cd"
   "abcd"
   7/23 - 31%
   

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9. string interpolation, normal
   a = 2
   b = "1#{a}3"
   p b
   123
   8/23 - 35%
   

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10. string interpolation, also normal
    @a = 5
    b = "4#{@a}6"
    p b
    456
    9/23 - 40%
    

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11. string interpolation, WTF?
    @a = 8
    b = "#@a"
    c = "7#@a"
    d = "7#@a9"
    p b
    p c
    p d
    8
    78
    7
    10/23 - 44%
    

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12. interpolate into symbols
    p :this_is_a_symbol.object_id
    klass = "symbol"
    p :"this_is_a_#{klass}".object_id
    333788
    333788
    11/23 - 48%
    

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13. string delimiters
    "String!"
    'String!'
    %{String!}
    %|String!|
    %`String!`
    %;String!;
    12/23 - 53%
    

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14. String#*
    # "*" * 80
    ******************************************
    13/23 - 57%
    

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15. DATA and __END__
    $ cat data.rb
    p YAML.load(DATA.read)[ARGV.first]
    __END__
    foo: "Bar"
    baz: "LOL!"
    $ ruby -ryaml data.rb
    nil
    $ ruby -ryaml data.rb foo
    "Bar"
    $ ruby -ryaml data.rb bar
    "LOL!"
    14/23 - 61%
    

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16. redo
    # s = ''
    ""
    # 1.upto(5) { |i| s << i.to_s; redo if s.size < 3 }
    1
    # s
    "1112345"
    15/23 - 66%
    

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17. pulling elements out of arrays
    # args = [1, 2, 3]
    # first, *rest = args
    # first
    1
    # rest
    [2, 3]
    16/23 - 70%
    

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18. splat arguments, anywhere (1.9+)
    # def foo(*args); p args; end
    # foo(1, 2, 3, 4)
    [1, 2, 3, 4]
    # def bar(first, *args); p first; p args; end
    # bar(1, 2, 3, 4)
    1
    [2, 3, 4]
    # def baz(first, *args, last); p first; p args; p last; end
    # baz(1, 2, 3, 4)
    1
    [2, 3]
    4
    17/23 - 74%
    

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19. destructuring arrays
    def touch_down
    yield [3, 7]
    puts "touchdown!"
    end
    touch_down do |(first_down, second_down)|
    puts "#{first_down} yards on the run"
    puts "#{second_down} yards passed"
    end
    3 yards on the run
    7 yards passed
    touchdown!
    18/23 - 79%
    

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20. Enumerable#any? / #all?
    # [false, false, true].any?
    true
    # [false, false, nil].any?
    false
    # [true, true, true].all?
    true
    # [true, true, false].all?
    false
    19/23 - 83%
    

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21. Hash#new with a block
    # smash = Hash.new { |hash, key|
    hash[key] = "a #{key} just got SMASHED!" }
    {}
    # smash[:plum] = "cannot smash."
    {:plum=>"cannot smash."}
    # smash[:watermelon]
    {:plum=>"cannot smash.",
    :watermelon=>"a watermelon just got SMASHED!"}
    20/23 - 87%
    

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22. Hash::[]
    # Hash[:apples, 3, :bananas, 2]
    {:apples=>3, :bananas=>2}
    # Hash[[:apples, 3, :bananas, 2] * 300_000]
    SystemStackError: stack level too deep
    Ruby bug warning!
    21/23 - 92%
    

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23. j and jj (1.9+)
    # require 'json'
    # h = {a: 1, b:2}
    {:a=>1, :b=>2}
    # j(h)
    {"a":1,"b":2}
    # jj(h)
    {
    "a": 1,
    "b": 2
    }
    22/23 - 96%
    

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