CODEWITHSUNDEEP
ruby
wotaskd
wotaskd

Reputation: 965

Getting a substring in Ruby by x number of chars

I'm trying to produce some Ruby code that will take a string and return a new one, with a number x number of characters removed from its end - these can be actual letters, numbers, spaces etc.

Ex: given the following string

a_string = "a1wer4zx"

I need a simple way to get the same string, minus - say - the 3 last characters. In the case above, that would be "a1wer". The way I'm doing it right now seems very convoluted:

an_array = a_string.split(//,(a_string.length-2))
an_array.pop
new_string = an_array.join

Any ideas?

Upvotes: 64

Views: 131713

Answers (6)

Nathan Derhake
Nathan Derhake

Reputation: 21

I know a lot of people already said this, but I think the best option is this:

'abcdefg'[0..-4] # should return 'abcd'

Something important to realize is that the returned string is inclusive on both endpoints. A lot of string parsing methods (e.g., the java and javascript substring method) are inclusive on the first endpoint and exclusive on the last, but this is NOT the case with the above way.

'abcdefghijklm'[1..5] # returns 'bcdef'


// substring method in java or javascript returns 'bcde'

'abcdefghijklm'.substring(1, 5);

Upvotes: 2

Paulo Fidalgo
Paulo Fidalgo

Reputation: 22331

Another option could be to use the slice method

a_string = "a1wer4zx"
a_string.slice(0..5) 
=> "a1wer4"

Documentation: http://ruby-doc.org/core-2.5.0/String.html#method-i-slice

Upvotes: 8

Aray Karjauv
Aray Karjauv

Reputation: 2945

if you need it in rails you can use first (source code)

s = '1234567890'
x = 4
s.first(s.length - x) # => "123456"

there is also last (source code)

s.last(2) # => "90"

alternatively check from/to

Upvotes: 3

Leo Brito
Leo Brito

Reputation: 2051

Another option is getting the list of chars of the string, takeing x chars and joining back to a string:

[13] pry(main)> 'abcdef'.chars.take(2).join
=> "ab"
[14] pry(main)> 'abcdef'.chars.take(20).join
=> "abcdef"

Upvotes: 2

Brian Clapper
Brian Clapper

Reputation: 26230

Use something like this:

s = "abcdef"
new_s = s[0..-2] # new_s = "abcde"

See the slice method here: http://ruby-doc.org/core/classes/String.html

Upvotes: 18

Nikita Rybak
Nikita Rybak

Reputation: 68046

How about this?

s[0, s.length - 3]

Or this

s[0..-4]

edit 

s = "abcdefghi"
puts s[0, s.length - 3]  # => abcdef
puts s[0..-4]            # => abcdef

Upvotes: 131

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