Truncate string when it is too long

Question

I have two strings:

short_string = \"hello world\"
long_string = \"this is a very long long long .... string\" # suppose more than 10000 chars

Answer 1

This is how Ruby on Rails does it in their String#truncate method as a monkey-patch:

class String
  def truncate(truncate_at, options = {})
    return dup unless length > truncate_at

    options[:omission] ||= '...'
    length_with_room_for_omission = truncate_at - options[:omission].length
    stop = if options[:separator]
      rindex(options[:separator], length_with_room_for_omission) || 
        length_with_room_for_omission
      else
        length_with_room_for_omission
      end

    "#{self[0...stop]}#{options[:omission]}"
  end
end

Then you can use it like this

'And they found that many people were sleeping better.'.truncate(25, omission: '... (continued)')
# => "And they f... (continued)"