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String#bitruncate

Posted on February 21, 2009 by Michael

And that’s ‘“bi-truncate” not “bit-uncate”.

What’s it do?

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"This is a test".bitruncate(:length => 6) ==> "Thi...est"
"This is a test".bitruncate(:elength => 6) ==> "...a test"

The default options are { :length => 30 } which will produce 15 characters from the front and 15 from the end, putting … marks in the middle.

For rails, I put this in my lib/core_extensions.rb file.

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#
# Copyright (c) 2009 Michael Graff.  All rights reserved.
#
# Redistribution and use in source and binary forms, with or
# without modification, are permitted provided that the following
# conditions are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above
#    copyright notice, this list of conditions and the following
#    disclaimer in the documentation and/or other materials provided
#    with the distribution.
# 3. The name of Michael Graff may not be used to endorse or promote
#    products derived from this software without specific prior
#    written permission.
#
# THIS SOFTWARE IS PROVIDED BY Michael Graff ``AS IS'' AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL Micahel Graff
# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
# OF SUCH DAMAGE.
#

class String
  #
  # Truncate from both ends of a string.  The :length parameter, which defaults
  # to 30, will return the first 15 and the last 15 characters from a string
  # if it is longer than 30 characters.  If it is shorter, the entire string
  # is returned.
  #
  # Another way to specify the front and back portions are with :flength and
  # :elength.  If you specify one of these but not the other then you will
  # not get the missing part.  e.g., :flength => 10 alone will return only
  # the first 10 charcters of the string.  This is the same as the standard
  # truncate(s, :length => 10) helper.
  #
  # If a :length parameter is provided it will override any other lengths
  # specified.
  #
  def bitruncate(options = {})
    maxlength = options[:length] || 0
    flength = options[:flength] || 0
    elength = options[:elength] || 0
    omission = options[:omission] || '...'

    if maxlength == 0 && flength == 0 && elength == 0
      maxlength = 30
    end
    if maxlength != 0
      flength = maxlength / 2
      elength = maxlength / 2
    end

    return self if length <= (flength + elength)

    front = ''
    back = ''
    if flength > 0
      front = self[0..(flength - 1)]
    end
    if elength > 0
      back = self[(length - elength)..(length)]
    end

    front + omission + back
  end
end
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