String Slicing. Ruby Method of the Month 2009.07. Lightning talk for the Columbus Ruby Brigade.

1. METHOD OF THE MONTH
Ruby’s String Slicing
Kevin Munc
@muncman

2. Have you ever wanted a
portion of a String?
COLUMBUS RUBY BRIGADE

3. “COLUMBUS RUBY
BRIGADE”.slice(5,8)

4. EXAMPLES

5. # The slice Method (start, length)
"abcdefghijklm".slice(5,3) => "fgh"
"0123456789".slice(5,3) => "567"

6. # The slice Method (start, length)
"abcdefghijklm".slice(5,3) => "fgh"
"0123456789".slice(5,3) => "567"
# Bracketed
"0123456789"[5,3] => "567"

7. # Ranges
"0123456789".slice(3..6) => "3456"
"0123456789".slice(3...6) => "345"

8. # Ranges
"0123456789".slice(3..6) => "3456"
"0123456789".slice(3...6) => "345"
"0123456789"[3..6] => "3456"
"0123456789"[3...6] => "345"

9. # With Negatives
"0123456789".slice(-4,3) => "678"
"0123456789".slice(-4..-2) => "678"

10. # With Negatives
"0123456789".slice(-4,3) => "678"
"0123456789".slice(-4..-2) => "678"
"0123456789".slice(5,-3) => nil
"0123456789".slice(-4..4) => ""

11. # With Negatives
"0123456789".slice(-4,3) => "678"
"0123456789".slice(-4..-2) => "678"
"0123456789".slice(5,-3) => nil
"0123456789".slice(-4..4) => ""
"0123456789"[10..10] => ""
"0123456789".[10,0] => ""

12. # Beyond Bounds
"0123456789".slice(8,100) => "89"
"0123456789".slice(12..14) => nil

13. # Regex
"0123456789"[/45/] => "45"
"0123456789".slice(/4.6/) => "456"
"0123456789".slice(/abc/) => nil

14. # With a single argument (index)
"0123456789".slice(0) => 48
"0123456789"[4] => 52
"0123456789".slice(10) => nil

15. # With a single argument (index)
"0123456789".slice(0) => 48
"0123456789"[4] => 52
"0123456789".slice(10) => nil
# ?4 => 52 and 52.chr => "4"

16. # With a single argument (index)
"0123456789".slice(0) => 48
"0123456789"[4] => 52
"0123456789".slice(10) => nil
# ?4 => 52 and 52.chr => "4"
# To get a single character
"0123456789".slice(4,1) => "4"
"0123456789"[3..3] => "3"

17. # With (sub-)Strings
"0123456789".slice("678") => "678"
"0123456789".slice("876") => nil

18. # With a Bang
seq = "0123456789"
=> "0123456789"

19. # With a Bang
seq = "0123456789"
=> "0123456789"
seq.slice(6..8) => "678"
seq => "0123456789"

20. # With a Bang
seq = "0123456789"
=> "0123456789"
seq.slice(6..8) => "678"
seq => "0123456789"
seq.slice!(6..8) => "678"
seq => "0123459"

21. # With a Bang, Progressively
bev = "orange juice"
=> "orange juice"

22. # With a Bang, Progressively
bev = "orange juice"
=> "orange juice"
bev.slice!("e") => "e"
bev => "orang juice"

23. # With a Bang, Progressively
bev = "orange juice"
=> "orange juice"
bev.slice!("e") => "e"
bev => "orang juice"
bev.slice!("e") => "e"
bev => "orang juic"

24. # With a Bang, Progressively
bev = "orange juice"
=> "orange juice"
bev.slice!("e") => "e"
bev => "orang juice"
bev.slice!("e") => "e"
bev => "orang juic"
bev.slice!("e") => nil

25. # Assignment, with Brackets Only
seq = "0123456789"
=> "0123456789"

26. # Assignment, with Brackets Only
seq = "0123456789"
=> "0123456789"
seq[0] = "a" => "a"
seq => "a123456789"

27. # Assignment, with Brackets Only
seq = "0123456789"
=> "0123456789"
seq[0] = "a" => "a"
seq => "a123456789"
seq[5,2] = "xy" => "xy"
seq => "a1234xy789"

28. # Assignment, continued
seq => "a1234xy789"

29. # Assignment, continued
seq => "a1234xy789"
seq[7,3] = "_" => "_"
seq => "a1234xy_"

30. # Assignment, continued
seq => "a1234xy789"
seq[7,3] = "_" => "_"
seq => "a1234xy_"
seq[3,2] = "LONG" => "LONG"
seq => "a12LONGxy_"

31. # Not just for Strings
myArray = [0,1,2,3,4,5,6,7,8,9]
=> [0,1,2,3,4,5,6,7,8,9]

32. # Not just for Strings
myArray = [0,1,2,3,4,5,6,7,8,9]
=> [0,1,2,3,4,5,6,7,8,9]
myArray.slice(2,3) => [2, 3, 4]
myArray[2..4] => [2, 3, 4]
myArray[0,5] = [9,8] => [9,8]
myArray => [9, 8, 5, 6, 7, 8, 9]

33. Try it yourself.
It’s completely
safe!

34. Questions? Answers?
Photo Sources:
http://www.flickr.com/photos/nickwheeleroz/2201057065/
http://www.flickr.com/photos/simpologist/42391997/
http://www.flickr.com/photos/uaeincredible/3234149448/
http://www.flickr.com/photos/mzaluska/3313083808/