CODEWITHSUNDEEP
rubystring
Steve
Steve

Reputation: 5073

string.split method in ruby behaves funny to me

txt = "1aaa5"

Then

txt.split("a") produces [1, "", "", 5] in ruby 1.9. Anyone can explain why? Particularly, why not [1, 5]? Thanks.

Upvotes: 2

Views: 799

Answers (6)

steenslag
steenslag

Reputation: 80065

If you don't specify a pattern to split on, split splits on whitespace. So, in addition to the other solutions, you could do

txt = "1aaa5"
txt.gsub('a',' ').split
=>[1, 5]

(if the text doesn't contain relevant whitespace).

Upvotes: 0

Jeriko
Jeriko

Reputation: 6637

When you call split, you're passing a delimiter which, by nature, is removed from the string when it's split.

Take, for example, the following:

s = ",foo"

When you call s.split(","), you're saying "Take everything on the left side of the comma and put it in it's own array entry, then take everything on the right side of the comma and put it in the next entry, ignoring the comma itself". The function sees "everything on the left of the comma" as "", not as nothing.

So your string follows the following pattern:

1aaa5
1, aa5
1, '', a5
1, '', '', 5

Which explains why there are two empty strings, and not just [1,5]

Upvotes: 2

YOU
YOU

Reputation: 123831

Because its split on every instance of "a"

  1. 1aaa5 splits into 1 and aa5
  2. aa5 splits into "" and a5
  3. a5 splits into "" and 5

so, 1, "", "", 5

use /a+/ or "aaa" instead

irb(main):002:0> txt.split(/a+/)
=> ["1", "5"]

Upvotes: 10

Allen George
Allen George

Reputation: 450

The behaviour you're seeing makes sense. When you call string.split("a") you're saying "use 'a' as the delimiter" and give me an array of the values between the delimiters. Between the first 'a' and the second 'a' in txt the value is an empty string; the same goes for the value between the second and third 'a'. That's why you see [1, "", "", 5]

It's as if txt were 1,,,5 and you chose ',' as the delimiter. If someone asked what values are in the list it'd be:

  1. 1
  2. empty
  3. empty
  4. 5

Upvotes: 2

tvanfosson
tvanfosson

Reputation: 532455

Because your delimiter is a and Ruby can't guess that you don't want null entries. Consider your example, but replace the a character with a comma.

txt = "1,,,5"

In my world, I might consider that 4 columns with zero values implied for the middle two. I certainly wouldn't want it to remove the empty entries, because then if there weren't 4, I wouldn't know which ones should be zeros.

Because it can't guess, it returns both the empty "fields" and non-empty "fields" in the array. Use @S.Mark's solution if you need it to omit the empty "fields."

Upvotes: 3

Beanish
Beanish

Reputation: 1662

Your delimiter "a" is present 3 times. Try splitting on "aaa" instead.

Upvotes: 0

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