What's the best way to cut a string if the length is above n characters?
Is it slice, or is there any other convenient method? Trying to
understand the string class from the docs but not sure which one to use.
--
Posted via http://www.ruby-forum.com/.
this_always_works = string[ 0 .. n ]
regardless of whether the string is <, =, or > than n
On Aug 19, 2008, at 9:25 AM, Pål Bergström wrote:
What's the best way to cut a string if the length is above n characters?
Is it slice, or is there any other convenient method? Trying to
understand the string class from the docs but not sure which one to use.
--
we can deny everything, except that we have the possibility of being better. simply reflect on that.
h.h. the 14th dalai lama
Rails has a utf8-compatible helper called truncate, called like so:
truncate(text, length = 30, truncate_string = "...")
If text is longer than length, text will be truncated to the length of
length (defaults to 30) and the last characters will be replaced with
the truncate_string (defaults to "...").
And the implementation is:
def truncate(text, length = 30, truncate_string = "...")
if text
l = length - truncate_string.chars.length
chars = text.chars
(chars.length > length ? chars[0...l] + truncate_string :
text).to_s
end
end
Where chars is a string method in Ruby 1.8.7 or greater.
On Aug 19, 11:25 am, Pål Bergström <p...@palbergstrom.com> wrote:
What's the best way to cut a string if the length is above n characters?
Is it slice, or is there any other convenient method? Trying to
understand the string class from the docs but not sure which one to use.
I believe slice! also always works:
irb(main):011:0> s="abcdefghijklmnop"
=> "abcdefghijklmnop"
irb(main):012:0> s.length
=> 16
irb(main):013:0> s.slice! 50..-1
=> nil
irb(main):014:0> s
=> "abcdefghijklmnop"
irb(main):015:0> s.slice! 5..-1
=> "fghijklmnop"
irb(main):016:0> s
=> "abcde"
It looks uglier but it modifies the string in place which might come in handy at times.
Kind regards
robert
On 19.08.2008 17:45, ara.t.howard wrote:
On Aug 19, 2008, at 9:25 AM, Pål Bergström wrote:
What's the best way to cut a string if the length is above n characters?
Is it slice, or is there any other convenient method? Trying to
understand the string class from the docs but not sure which one to use.this_always_works = string[ 0 .. n ]
regardless of whether the string is <, =, or > than n
Ara Howard wrote:
On Aug 19, 2008, at 9:25 AM, P�l Bergstr�m wrote:
What's the best way to cut a string if the length is above n
characters?
Is it slice, or is there any other convenient method? Trying to
understand the string class from the docs but not sure which one to
use.this_always_works = string[ 0 .. n ]
regardless of whether the string is <, =, or > than n
Found a problem with this. It messes up swedish letters that, I guess,
is cut right of as if they where handled as latin1. What method can
handle utf-8?
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Mark Thomas wrote:
Rails has a utf8-compatible helper called truncate, called like so:
truncate(text, length = 30, truncate_string = "...")
If text is longer than length, text will be truncated to the length of
length (defaults to 30) and the last characters will be replaced with
the truncate_string (defaults to "...").And the implementation is:
def truncate(text, length = 30, truncate_string = "...")
if text
l = length - truncate_string.chars.length
chars = text.chars
(chars.length > length ? chars[0...l] + truncate_string :
text).to_s
end
endWhere chars is a string method in Ruby 1.8.7 or greater.
Perfect 
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Pål Bergström wrote:
Don't say I've run into a classic encoding issue. 
Does Ruby have a problem with utf8 support?
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Posted via http://www.ruby-forum.com/.
Pål Bergström wrote:
Don't say I've run into a classic encoding issue.
Does Ruby have a problem with utf8 support?
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Posted via http://www.ruby-forum.com/\.
I did this for a project (way back in Rails 1.1.6)
$KCODE = 'UTF8'
require 'jcode'
class String
def first(limit = 1)
self.match(%r{^(.{0,#{limit}})})[1]
end
end
You'd still have to assign this, but:
name = "P\303\245l Bergstr\303\266m"
=> "P\303\245l Bergstr\303\266m"
puts name
Pål Bergström
=> nil
puts name.first(2)
På
=> nil
puts name.first(3)
Pål
=> nil
puts name.first(12)
Pål Bergströ
=> nil
puts name[0...12]
Pål Bergstr
=> nil
puts name[0...2]
P?
=> nil
p name[0...2]
"P\303"
=> nil
I hope that helps you.
-Rob
Rob Biedenharn http://agileconsultingllc.com
Rob@AgileConsultingLLC.com
On Aug 19, 2008, at 1:42 PM, Pål Bergström wrote:
This seems to do the trick. Will it always work?
lastspace = message.message[0..70].rindex(" ")
puts message.message[0..lastspace.to_i]
--
Posted via http://www.ruby-forum.com/.
You likely want an exclusive range unless you want the space at the end.
message.message[0...lastspace.to_i]
What if there's no space? Then perhaps:
message.message[0..(lastspace || -1).to_i]
Of course, that puts you back in the position of getting the full string rather than some truncated version with no more than your desired number of characters.
-Rob
Rob Biedenharn http://agileconsultingllc.com
Rob@AgileConsultingLLC.com
On Aug 19, 2008, at 4:08 PM, Pål Bergström wrote:
This seems to do the trick. Will it always work?
lastspace = message.message[0..70].rindex(" ")
puts message.message[0..lastspace.to_i]
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.
I get the feeling that a solution using regular expressions might be more efficient and also easier in your case. Maybe any of
str.sub! %r{\A(.{50}).*\z}, '\\1'
str.sub! %r{\A(.{1,50})(?: .*)?\z}, '\\1'
str.sub! %r{\s\S*\z}, ''
Depends on your string contents of course.
Kind regards
robert
On 19.08.2008 22:33, Rob Biedenharn wrote:
On Aug 19, 2008, at 4:08 PM, Pål Bergström wrote:
This seems to do the trick. Will it always work?
lastspace = message.message[0..70].rindex(" ")
puts message.message[0..lastspace.to_i]You likely want an exclusive range unless you want the space at the end.
message.message[0...lastspace.to_i]
What if there's no space? Then perhaps:
message.message[0..(lastspace || -1).to_i]
Of course, that puts you back in the position of getting the full string rather than some truncated version with no more than your desired number of characters.
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.I get the feeling that a solution using regular expressions might be
more efficient and also easier in your case. Maybe any ofstr.sub! %r{\A(.{50}).*\z}, '\\1'
str.sub! %r{\A(.{1,50})(?: .*)?\z}, '\\1'
str.sub! %r{\s\S*\z}, ''Depends on your string contents of course.
Kind regards
robert
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).
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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
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
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).
--
use.inject do |as, often| as.you_can - without end
How about:
s[0..70].gsub(/\s?\S*$/,'')
Mark Thomas wrote:
How about:
s[0..70].gsub(/\s?\S*$/,'')
I'll try it.
--
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