StringFormatter is a method for defining custom strf-style methods for your object.

* string_formatter require Ruby 1.9 or higher *

Example:

class PersonFormatter < StringFormatter
  
  f { |p| p.first_name }
  F { |p| p.first_name.upcase }
  l { |p| p.last_name  }

  punctuation

  pipe { |p| 'PIPE' }
  
end

class UpcaseFormatter < StringFormatter
  
  f { |p| p.first_name.upcase }
  l { |p| p.last_name.upcase  }
  
end

class Person
  attr_accessor :first_name, :last_name

  define_format_string :strf,   :with => PersonFormatter
  define_format_string :strfup, :with => UpcaseFormatter
  
  def initialize(*names)
    @first_name, @last_name = names
  end
  
end

p = Person.new("Bob", "Smith")

p.strf('%l, %f %|')
# => "Smith, Bob PIPE"

p.strfup('%l, %f')
# => "SMITH, BOB"

You can define definitions for lower case characters, upper case characters, and punctuation marks.  The method for lower and upper case characters is the character itself, and the punctuation marks have specific names for each.