Truncate string to the first n words

Question

What\'s the best way to truncate a string to the first n words?

Answer 1

You can use str.split.first(n).join(' ') with n being any number.

Contiguous white spaces in the original string are replaced with a single white space in the returned string.

For example, try this in irb:

>> a='apple    orange pear banana   pineaple  grapes'
=> "apple    orange pear banana   pineaple  grapes"
>> b=a.split.first(2).join(' ')
=> "apple orange"

This syntax is very clear (as it doesn't use regular expression, array slice by index). If you program in Ruby, you know that clarity is an important stylistic choice.

A shorthand for join is * So this syntax str.split.first(n) * ' ' is equivalent and shorter (more idiomatic, less clear for the uninitiated).

You can also use take instead of first so the following would do the same thing

a.split.take(2) * ' '

Answer 2

This could be following if it's from rails 4.2 (which has truncate_words)

string_given.squish.truncate_words(number_given, omission: "")

Answer 3

You could do it like this:

s     = "what's the best way to truncate a ruby string to the first n words?"
n     = 6
trunc = s[/(\S+\s+){#{n}}/].strip

if you don't mind making a copy.

You could also apply Sawa's Improvement (wish I was still a mathematician, that would be a great name for a theorem) by adjusting the whitespace detection:

trunc = s[/(\s*\S+){#{n}}/]

If you have to deal with an n that is greater than the number of words in s then you could use this variant:

s[/(\S+(\s+)?){,#{n}}/].strip

Answer 4

n = 3
str = "your long    long   input string or whatever"
str.split[0...n].join(' ')
 => "your long long"


str.split[0...n] # note that there are three dots, which excludes n
 => ["your", "long", "long"]