Last n Characters of a Ruby String
Almost without fail people come to me after using Ruby for a while and ask if there is any easy way to get the last n characters of a string. The easiest way to do it without extending classes is:
str = 'This is a test'
srt[-4,4] # => 'test'However if you are willing to mixin a nice little method you will forevermore have rapid access to the last characters of a string.
module LastN
def last(n)
self[-n,n]
end
end
class String
include LastN
end
'This is a test'.last(4) # => 'test'Enjoy!
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posted by Lucas Carlson at
9:10 PM
7 Comments:
Um, the #last methods on Array and String already do that in Ruby.
10:41 PM, June 08, 2006
You mean Array and Range? String doesn't have #last and Range#last has no arguments, its actually Range#end
irb(main):006:0> [1,2,3,4,5].last(2)
=> [4, 5]
irb(main):007:0> "hello".last(2)
NoMethodError: undefined method `last' for "hello":String
from (irb):7
from :0
irb(main):008:0> (0..5).last(2)
ArgumentError: wrong number of arguments (1 for 0)
from (irb):8:in `last'
from (irb):8
from :0
irb(main):009:0> (0..5).last
=> 5
11:21 PM, June 08, 2006
D'oh! I was using the Rails console. ActiveSupport adds the String method for last(n). But Ruby 1.8.4 includes it for Array already.
10:12 AM, June 09, 2006
It's in ruby 1.8.3 aswell!
6:26 AM, October 01, 2006
You could also directly add the last(n) function to the String class
class String
def last(n)
self[-n,n]
end
end
"This works too".last(3) # => "too"
5:59 AM, April 13, 2010
The ActiveSupport version also works when the length you want to clip to is greater than the length of the string, e.g.
"short string".last(20) -> "short string"
whereas your function will return nil
10:44 AM, June 06, 2011
yeah this returns nil if you give it too low a number. Which is really ruby's bug but hey...
4:24 AM, January 20, 2012
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