Ruby Method of the Month 2010.07. Lightning talk for the Columbus Ruby Brigade.

1. cycle
Method of the Month
Kevin Munc
@muncman

2. cycle
It cycles through the values
fed to it, returning one
value each invocation, over
and over.

3. ActionView::Helpers::TextHelper

4. Console Setup
irb --> require 'active_support'
==> true
irb --> require 'action_view'
==> ["ActionView"]
irb --> class Object
>> include ActionView::Helpers::TextHelper
>> end
==> Object

5. Simple Example
> items = (1..6).to_a
==> [1, 2, 3, 4, 5, 6]
> items.each { |i| puts "#{i}: #{cycle('odd','even')}" }
1: odd
2: even
3: odd
4: even
5: odd
6: even

6. With More Elements
> items.each do |i|
puts "#{i}: #{cycle('odd','even','chunky','bacon')}"
end
1: odd
2: even
3: chunky
4: bacon
5: odd
6: even

7. Mo’ Methods, Mo’ Examples
reset_cycle
current_cycle
irb --> set_one = [0,1,2]
==> [0, 1, 2]
irb --> set_two = %w{a b c}
==> ["a", "b", "c"]

8. Multiple Cycles w/ Naming
set_one.each do |s1|
prefix = cycle('even','odd', :name => 'outer')
set_two.each do |s2|
suffix = cycle('yin','yang', :name => 'inner')
puts "#{prefix} #{s1} #{s2} #{suffix}"
end
end

9. Multiple Cycles w/ Naming
set_one.each do |s1| even 0 a yin
prefix = cycle('even','odd', :name => 'outer') even 0 b yang
set_two.each do |s2| even 0 c yin
suffix = cycle('yin','yang', :name => 'inner') odd 1 a yang
puts "#{prefix} #{s1} #{s2} #{suffix}" odd 1 b yin
end odd 1 c yang
end even 2 a yin
even 2 b yang
even 2 c yin

10. Restarting Named Cycles
set_one.each do |s1|
prefix = cycle('even','odd', :name => 'outer')
set_two.each do |s2|
suffix = cycle('yin','yang', :name => 'inner')
puts "#{prefix} #{s1} #{s2} #{suffix}"
end
reset_cycle('inner')
end

11. Restarting Named Cycles
set_one.each do |s1| even 0 a yin
prefix = cycle('even','odd', :name => 'outer') even 0 b yang
set_two.each do |s2| even 0 c yin
suffix = cycle('yin','yang', :name => 'inner') odd 1 a yin
puts "#{prefix} #{s1} #{s2} #{suffix}" odd 1 b yang
end odd 1 c yin
reset_cycle('inner') even 2 a yin
end even 2 b yang
even 2 c yin

12. reset_cycle('inner')
reset_cycle('outer')

13. Get the cycle w/out advancing?
set_one.each do |s1|
puts "#{s1} - #{cycle('on','off')}"
puts "#{s1} - #{cycle('on','off')}"
end

14. Get the cycle w/out advancing?
set_one.each do |s1| 0 - on
puts "#{s1} - #{cycle('on','off')}" 0 - off
puts "#{s1} - #{cycle('on','off')}" 1 - on
end 1 - off
2 - on
2 - off

15. Get the cycle w/out advancing?
set_one.each do |s1| 0 - on
puts "#{s1} - #{cycle('on','off')}" 0 - off
puts "#{s1} - #{cycle('on','off')}" 1 - on
end 1 - off
2 - on
Nope. 2 - off

16. Get the cycle w/out advancing?
set_one.each do |s1|
puts "#{s1} - #{cycle('on','off')}"
puts "#{s1} - #{current_cycle}"
end

17. Get the cycle w/out advancing?
set_one.each do |s1| 0 - on
puts "#{s1} - #{cycle('on','off')}" 0 - on
puts "#{s1} - #{current_cycle}" 1 - off
end 1 - off
2 - on
2 - on

18. Get the cycle w/out advancing?
set_one.each do |s1| 0 - on
puts "#{s1} - #{cycle('on','off')}" 0 - on
puts "#{s1} - #{current_cycle}" 1 - off
end 1 - off
2 - on
Yep. 2 - on

19. Another Example
set_one.each do |s1|
cycle('ruby','rails','bacon', :name => 'outer')
set_two.each do |s2|
puts "Inner: #{cycle('C','R','B', :name => 'inner')}
and Outer is still #{current_cycle('outer')}"
end
end

20. Another Example
set_one.each do |s1|
cycle('ruby','rails','bacon', :name => 'outer')
set_two.each do |s2|
puts "Inner: #{cycle('C','R','B', :name => 'inner')}
and Outer is still #{current_cycle('outer')}"
end
Inner: C and Outer is still ruby
end
Inner: R and Outer is still ruby
Inner: B and Outer is still ruby
Inner: C and Outer is still rails
Inner: R and Outer is still rails
Inner: B and Outer is still rails
Inner: C and Outer is still bacon
Inner: R and Outer is still bacon
Inner: B and Outer is still bacon

21. The cycle method
In Rails (not Array#cycle)
Often used to ‘zebra stripe’ table rows
Supported by:
reset_cycle
current_cycle
cycle names (default is ‘default’)

22. RRBO.com uses many methods!

23. Don’t forget to check out rrbo.com !
Questions?
Photo Credits
http://www.flickr.com/photos/falconmotorcycles/3556349741/
http://www.flickr.com/photos/falconmotorcycles/3556350229/
http://www.flickr.com/photos/falconmotorcycles/3556345789/
http://www.flickr.com/photos/falconmotorcycles/3557161910/
http://www.flickr.com/photos/balakov/3494949386/