Cut a string if length > n

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.

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

a @ http://codeforpeople.com/

On 19.08.2008 17:45, ara.t.howard wrote:

regardless of whether the string is <, =, or > than n

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

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

a @ http://codeforpeople.com/

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?

Pål Bergström wrote:

Don’t say I’ve run into a classic encoding issue. :frowning:

Does Ruby have a problem with utf8 support?

On Aug 19, 2008, at 1:42 PM, Pål Bergström wrote:

Pål Bergström wrote:

Don’t say I’ve run into a classic encoding issue. :frowning:

Does Ruby have a problem with utf8 support?

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:

irb> name = “P\303\245l Bergstr\303\266m”
=> “P\303\245l Bergstr\303\266m”
irb> puts name
Pål Bergström=> nil
irb> puts name.first(2)

=> nil
irb> puts name.first(3)
Pål=> nil
irb> puts name.first(12)
Pål Bergströ
=> nil
irb> puts name[0…12]
Pål Bergstr
=> nil
irb> puts name[0…2]
P?
=> nil
irb> p name[0…2]
“P\303”
=> nil

I hope that helps you.

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

This seems to do the trick. Will it always work?

lastspace = message.message[0…70].rindex(" ")
puts message.message[0…lastspace.to_i]

On Aug 19, 11:25 am, Pål Bergström [email protected] 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.

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.

Mark T. 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
end

Where chars is a string method in Ruby 1.8.7 or greater.

Perfect :slight_smile:

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.

-Rob

Rob B. http://agileconsultingllc.com
[email protected]

On 19.08.2008 22:33, Rob B. wrote:

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.

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

Robert K. 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 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

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 :slight_smile: 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).

2008/8/20 Pål Bergström [email protected]:

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 :slight_smile: 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

How about:

s[0…70].gsub(/\s?\S*$/,’’)

Mark T. wrote:

How about:

s[0…70].gsub(/\s?\S*$/,’’)

I’ll try it.

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