Class: Text::Format::Alpha

Inherits:
Object
  • Object
show all
Defined in:
lib/text/format/alpha.rb

Overview

Provides a numbering object that will produce letters. Accepts four options for numbering that will control how the letters are presented when given as #[](index). This numbering object will only provide 26 values (“a” .. “z”) unless :wrap is true.

:transform

The symbol representing the method to be called on the letter. This must be a method that does not require any arguments.

:postfix

The value that will be appended to the letter presented by #[]. Defaults to nil.

:prefix

The value that will be prepended to the letter presented by #[]. Defaults to nil.

:wrap

If true, then indexes will be wrapped from “z” to “a”.

a1 = Text::Format::Alpha.new(:postfix => ".")
puts a1[0]  # => "a."
puts a1[1]  # => "b.
puts a1[27] # => ""

a2 = Text::Format::Alpha.new(:prefix => "A.")
puts a2[0]  # => "A.a"
puts a2[1]  # => "A.b"
puts a2[27] # => ""

a3 = Text::Format::Alpha.new(:transform => :upcase)
puts a3[0]  # => "A"
puts a3[1]  # => "B"
puts a3[27] # => ""

a4 = Text::Format::Alpha.new(:wrap => true)
puts a4[0]  # => "a"
puts a4[27] # => "b"

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ Alpha

:yields self:



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# File 'lib/text/format/alpha.rb', line 55

def initialize(options = {}) #:yields self:
  @transform  = options[:transform] || nil
  @wrap       = options[:wrap]      || false
  @postfix    = options[:postfix]   || nil
  @prefix     = options[:prefix]    || nil
end

Instance Method Details

#[](index) ⇒ Object 



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# File 'lib/text/format/alpha.rb', line 35

def [](index)
  if @wrap
    ltr = (?a + (index % 26)).chr
  elsif index.between?(0, 25)
    ltr = (?a + index).chr
  else
    ltr = nil
  end

  if ltr
    if @transform
      "#{@prefix}#{ltr.send(transform)}#{@postfix}"
    else
      "#{@prefix}#{ltr}#{@postfix}"
    end
  else
    ""
  end
end