From: Robert Klemme <shortcutter@...>
Date: 2008-08-20T16:36:11+09:00
Subject: Re: Cut a string if length > n

2008/8/20 Pål Bergström <pal@palbergstrom.com>:
> Robert Klemme wrote:
>
>> Pal, it seems we haven't seen the complete specification of what you
>> want to do.  It seems that not only length is a condition but also
>> positions of spaces.
>
> Hi. My app shows data in a list from a table called messages but only a
> fragment of it if it's to long.
>
> My solution seems to work fine. What do you think of it? Will it always
> work?
>
> lastspace = message.message[0..70].rindex(" ")
> puts message.message[0..lastspace.to_i]
>
> It doesn't do anything for non existing messages and text that isn't
> that long as 70. And it finds the last space. We might have long words
> in Swedish, but not that long :-) There will always be a space somewhere
> in the end where it can cut it without cutting and leave strange
> question marks as it cuts a swedish character (as Latin1 I guess).

As has been mentioned you probably should use the ... range form
because otherwise you'll have a space at the end.  But this does not
work in light of multiple spaces either.  I'd probably choose a
solution with regular expressions:

09:36:10 RKlemme$ /c/Temp/truncate.rb
["aaaaa", 5, "a", "", "aaaaa", "aaaaa", "aaaaa"]
["aaaaa bbbbb", 11, "aaaaa ", "aaaaa", "aaaaa bbbbb", "aaaaa bbbbb", "aaaaa"]
["aaaaa bbbbb ccccc", 17, "aaaaa bbbbb ", "aaaaa bbbbb", "aaaaa bbbbb
", "aaaaa bbbbb", "aaaaa bbbbb"]
["aaaaa bbbbb ccccc ddddd", 23, "aaaaa bbbbb ", "aaaaa bbbbb", "aaaaa
bbbbb ", "aaaaa bbbbb", "aaaaa bbbbb"]
["aaaaa", 5, "a", "", "aaaaa", "aaaaa", "aaaaa"]
["aaaaa  bbbbb", 12, "aaaaa  ", "aaaaa ", "aaaaa  bbbbb", "aaaaa
bbbbb", "aaaaa "]
["aaaaa  bbbbb  ccccc", 19, "aaaaa  ", "aaaaa ", "aaaaa  ", "aaaaa
bbbbb", "aaaaa  bbbbb"]
["aaaaa  bbbbb  ccccc  ddddd", 26, "aaaaa  ", "aaaaa ", "aaaaa  ",
"aaaaa  bbbbb", "aaaaa  bbbbb"]

Here's the code that you can use to play around with various solutions:

09:37:02 RKlemme$ cat /c/Temp/truncate.rb
#!/bin/env ruby

WD = 5
LIM = 12

strings = (0..3).map do |i|
  (0..i).map do |ii|
    (?a + ii).chr * WD
  end.join " "
end

strings.concat strings.map {|s| s.gsub /\s/, '  '}

strings.each do |str|
  p [
    str,
    str.length,
    str[0..str[0...LIM].rindex(' ').to_i],
    str[0...str[0...LIM].rindex(' ').to_i],
    str[%r{\A.{0,#{LIM}}\b(?!\s)}],
    str[%r{\A.{0,#{LIM - 1}}\S}], # <- my choice
    str[%r{\A(.{0,#{LIM}})\s}, 1] || str,
  ]
end

Kind regards

robert



-- 
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