Indexed KVO-Compliance & MacRuby

attr_indexed.rb

class Object
  def self.attr_indexed var, custom_methods = {}
    key = var.to_s
    capitalized_key = key.capitalize[0] + key[1..-1]
        
    methods = {
      :size => lambda { instance_variable_get("@#{var}").size },
      :at => lambda { |idx| instance_variable_get("@#{var}")[idx] },
      :insert => lambda { |obj, idx| instance_variable_get("@#{var}").insert(idx, obj) },
      :delete_at => lambda { |idx| instance_variable_get("@#{var}").delete_at(idx) }
    }.merge custom_methods
    
    define_method :"countOf#{capitalized_key}", methods[:size]
    define_method :"objectIn#{capitalized_key}AtIndex:", methods[:at]

    # define_method :"insertObject:in#{capitalized_key}AtIndex:", methods[:insert]
    # define_method :"removeObjectFrom#{capitalized_key}AtIndex:", methods[:delete_at]
  end
end

class Test  
  def initialize
    @squares = [0, 1, 4, 9, 16]
  end
  
  # backed by Array
  attr_indexed :squares
  
  # backed by custom methods
  attr_indexed :naturalNumbers, {
    :size => lambda { 4 },
    :at => lambda {|i| i }
  }
  
  # just straight KVO compliance
  def countOfCubes; 6; end
  def objectInCubesAtIndex(idx); idx ** 3; end
end

test = Test.new

# this is all correct
puts "count of natural numbers: #{test.countOfNaturalNumbers} == 4"
puts "count of squares: #{test.countOfSquares} == 5"
puts "count of cubes: #{test.countOfCubes} == 6"

# as are these...
puts "natural: #{test.objectInNaturalNumbersAtIndex(0)} == 0"
puts "squares: #{test.objectInSquaresAtIndex(3)} == 3 ** 2"
puts "cubes: #{test.objectInCubesAtIndex(5)} == 5 ** 3"

# this will fail, uncomment to fail.
puts "#{test.valueForKey("naturalNumbers")} == #{(0...4).to_a}"
puts "#{test.valueForKey("squares")} == #{(0...5).map { |i| i ** 2}}"

# this will work
puts "#{test.valueForKey("cubes")} == #{(0...6).map { |i| i ** 3}}"