Ruby Method of the Month 2010.02. Lightning talk for the Columbus Ruby Brigade.

1. Gr ou
pi ng
Ruby Method of the Month
Kevin Munc - @muncman

2. in_groups
in_groups_of

3. r
o s t
p n
p o
e e u si
S n
t
c Exiv t
A e y
a g
r
o :Ar i r n
: :C : p
r o u
: :G
http://api.rubyonrails.org/classes/ActiveSupport/CoreExtensions/Array/Grouping.html

4. Arrays into Groups

5. Follow Along in IRB!
• You’re going to need to use ActiveSupport:
•require ‘active_support’
• Note: require ‘activesupport’ (no underscore) is deprecated
for removal in Rails 3.

6. A Colorful Array
seq = %w{turquoise ultramarine chartreuse
lavender crimson burgundy coral teal magenta
maroon cerulean fuchsia emerald taupe auburn
vermillion}
seq.size
=> 16

7. in_groups
seq.in_groups(4)
=>
[
["turquoise", "ultramarine", "chartreuse",
"lavender"],
["crimson", "burgundy", "coral", "teal"],
["magenta", "maroon", "cerulean", "fuchsia"],
["emerald", "taupe", "auburn", "vermillion"]
]

8. in_groups_of
seq.in_groups_of(4)
=>
[
["turquoise", "ultramarine", "chartreuse",
"lavender"],
["crimson", "burgundy", "coral", "teal"],
["magenta", "maroon", "cerulean", "fuchsia"],
["emerald", "taupe", "auburn", "vermillion"]
]

9. in_groups
seq.in_groups(3)
=>
[
["turquoise", "ultramarine", "chartreuse",
"lavender", "crimson", "burgundy"],
["coral", "teal", "magenta", "maroon", "cerulean",
nil],
["fuchsia", "emerald", "taupe", "auburn",
"vermillion", nil]
]

10. in_groups_of
seq.in_groups_of(3)
=>
[
["turquoise", "ultramarine", "chartreuse"],
["lavender", "crimson", "burgundy"],
["coral", "teal", "magenta"],
["maroon", "cerulean", "fuchsia"],
["emerald", "taupe", "auburn"],
["vermillion", nil, nil]
]

11. in_groups with false
seq.in_groups(3, false)
=>
[
["turquoise", "ultramarine", "chartreuse",
"lavender", "crimson", "burgundy"],
["coral", "teal", "magenta", "maroon", "cerulean"],
["fuchsia", "emerald", "taupe", "auburn",
"vermillion"]
]

12. in_groups_of with false
seq.in_groups_of(3, false)
=>
[
["turquoise", "ultramarine", "chartreuse"],
["lavender", "crimson", "burgundy"],
["coral", "teal", "magenta"],
["maroon", "cerulean", "fuchsia"],
["emerald", "taupe", "auburn"],
["vermillion"]
]

13. in_groups with filler
seq.in_groups(3, 'white')
=>
[
["turquoise", "ultramarine", "chartreuse",
"lavender", "crimson", "burgundy"],
["coral", "teal", "magenta", "maroon", "cerulean",
"white"],
["fuchsia", "emerald", "taupe", "auburn",
"vermillion", "white"]
]

14. in_groups_of with filler
seq.in_groups_of(3, 'white')
=>
[
["turquoise", "ultramarine", "chartreuse"],
["lavender", "crimson", "burgundy"],
["coral", "teal", "magenta"],
["maroon", "cerulean", "fuchsia"],
["emerald", "taupe", "auburn"],
["vermillion", "white", "white"]
]

15. Warning:
The next two slides
have
Information
Overload

16. Another Look:
in_groups
gen = []; 20.times { |i| gen << i+1 }; gen
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
gen.in_groups(4) # into four groups
=> [[1, 2, 3, 4, 5], [6, 7, 8, 9, 10], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20]]
gen.in_groups(3) # into three groups
=> [[1, 2, 3, 4, 5, 6, 7], [8, 9, 10, 11, 12, 13, 14], [15, 16, 17, 18, 19, 20, nil]]
gen.in_groups(3, false) # into three groups, unpadded
=> [[1, 2, 3, 4, 5, 6, 7], [8, 9, 10, 11, 12, 13, 14], [15, 16, 17, 18, 19, 20]]
gen.in_groups(3, 99) # into three groups, with filler
=> [[1, 2, 3, 4, 5, 6, 7], [8, 9, 10, 11, 12, 13, 14], [15, 16, 17, 18, 19, 20, 99]]

17. Another Look:
in_groups_of
gen = []; 20.times { |i| gen << i+1 }; gen
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
gen.in_groups_of(4) # into groups of four
=> [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16], [17, 18, 19, 20]]
gen.in_groups_of(3) # into groups of three
=> [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12], [13, 14, 15], [16, 17, 18], [19, 20, nil]]
gen.in_groups_of(3, false) # into groups of three, unpadded
=> [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12], [13, 14, 15], [16, 17, 18], [19, 20]]
gen.in_groups_of(3, 99) # into groups of three, with filler
=> [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12], [13, 14, 15], [16, 17, 18], [19, 20, 99]]

18. Bonus Method!

19. split
• Divide an array based on:
• delimiter
• or block
• but not both
• a block is used if present
• This is the third and final method in
ActiveSupport::CoreExtensions::Array::
Grouping

20. split it. split it good!
a_ray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a_ray.split(5)
=> [[1, 2, 3, 4], [6, 7, 8, 9, 10]]

21. split it. split it good!
a_ray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a_ray.split(5)
=> [[1, 2, 3, 4], [6, 7, 8, 9, 10]]
b_ray = [1, 2, 3, 4, 5, 1, 2, 3, 4, 5]
b_ray.split(3)
=> [[1, 2], [4, 5, 1, 2], [4, 5]]

22. split it like it’s hot
a_ray
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a_ray.split { |elem| elem % 2 == 0 }
=> [[1], [3], [5], [7], [9], []]

23. split it like it’s hot
a_ray
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a_ray.split { |elem| elem % 2 == 0 }
=> [[1], [3], [5], [7], [9], []]
a_ray
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
a_ray.split { |elem| elem % 2 == 1 }
=> [[], [2], [4], [6], [8], [10]]

24. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5]
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

25. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5] Matches are
excluded, starting a
new array group.
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

26. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5] Matches are
excluded, starting a
new array group.
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
3
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

27. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5] Matches are
excluded, starting a
new array group.
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
3 4
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

28. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5] Matches are
excluded, starting a
new array group.
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
3 4 5
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

29. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5] Matches are
excluded, starting a
new array group.
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
3 4 5 3
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

30. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5] Matches are
excluded, starting a
new array group.
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
3 4 5 3 4
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

31. splitting hairs
b_ray
=> [1, 2, 3, 4, 5, 1, 2, 3, 4, 5] Matches are
excluded, starting a
new array group.
b_ray.split do |elem|
(3..5).include? elem
end
=> [[1, 2], [], [], [1, 2], [], [], []]
3 4 5 3 4 5
# File activesupport/lib/active_support/core_ext/array/grouping.rb, line 90
90: def split(value = nil)
91: using_block = block_given?
92:
93: inject([[]]) do |results, element|
94: if (using_block && yield(element)) || (value == element)
95: results << []
96: else
97: results.last << element
98: end
99:
100: results

32. Questions?
Image Credits
all from clickykbd@flickr
http://www.flickr.com/photos/clickykbd