Rails - Dec 2009 - to_hash

#
# Author : Jason Wang
# Date : 2009/28/12
# mailto: hxpwork-KN7UnAbNpbg@public.gmane.org
#
# The code convert an array to hash by specified method of the object in
the array.
#
# Examples
#  class Address
#    attr_accessor :street, :city
#    def initialize(street, city)
#      @street = street
#      @city = city
#    end
#  end
#  class Info
#    attr_accessor :name, :code, :place, :age
#    def initialize(name, code, place=nil)
#      @name = name
#      @code = code
#      @place = place
#      @age = 25
#    end
#  end
#  def get_info_array
#    return Array.new([
#        Info.new("Jason","111",
Address.new("long","gz")),
#        Info.new("Pony","222",
Address.new("chang","gz")),
#        Info.new("Jason","333",
Address.new("short","gx"))])
#  end
#
#  arr = get_info_array
#
#  then, you can use like that..
#
#  1) arr.to_hash({ :key => "name" })
#     hash --> { "Jason" => arr[2] , "Pony" =>
arr[1] }
#     **note: if key repeat, later value covered before value
#
#  2) arr.to_hash({ :key => "name", :value =>"code" })
#     hash --> { "Jason" => "333" , "Pony"
=> "222" }
#
#  3) arr.to_hash({ :key1 => "name" , :key2 => "code"
, :value =>
"place.city" })
#     hash --> { "Jason-111" => "gz" ,
"Pony-222" => "gz" , "Jason-333"
=> "gx" }
#
#  4) arr.to_hash_array( { :key => "name" } )
#     hash --> { "Jason" => [ arr[0], arr[2] ] ,
"Pony" => [ arr[1] ]
#     **note: if key repeat, later value append to array
#
#  5) arr.to_hash_array({ :key => "name", :value
=>"code" })
#     hash --> { "Jason" => [ "111" , "333"
] , "Pony" => [ "222" ] }
#
#  6) arr.to_hash_array({ :key1 => "name" , :key2 =>
"code" , :value =>
"place.city" })
#     hash --> { "Jason-111" => ["gz"] ,
"Pony-222" => ["gz"] ,
"Jason-333" => ["gx"] }
#
module Enumerable
  def to_hash( params )
    dict_block(self,params){ |dict,obj,params|
hash_get_key_value(obj,params) { |key,value| dict[key] = value } }
  end

  def to_hash_array(params)
    dict_block(self,params){ |dict,obj,params|
hash_get_key_value(obj,params) { |key,value| dict_array(dict,value,key)
} }
  end

  private

  def hash_get_key_value(obj, params)
    return if params.nil?
    key = get_method_key(obj,params[:key]) if params.include?(:key)
    key = get_two_key(obj,params[:key1],params[:key2]) if
params.include?(:key1) && params.include?(:key2)
    return if key.nil?
    obj = get_method_key(obj,params[:value]) unless params[:value].nil?
    yield key , obj
  end

  def dict_block(list, params)
    dict = Hash.new
    return dict if list.nil?
    if ( list.methods.include?("each"))
      list.each do |obj|
        yield dict, obj, params
      end
    else
      yield dict, list, params
    end
    dict
  end

  def dict_array(dict,obj,key)
    return if key.nil?
    dict.has_key?(key) ? dict[key] << obj : dict[key] = Array.new([obj])
  end

  def get_two_key(obj,key1,key2)
    key1_value = get_method_key(obj,key1)
    key2_value = get_method_key(obj,key2)
    return nil if key1_value.nil? || key2_value.nil?
    "#{key1_value}-#{key2_value}"
  end

  def get_method_key( obj, methodName )
    return nil if methodName.nil?
    methodName.split(".").each do |m_name|
      return nil unless obj.methods.include?(m_name)
      obj = obj.method(m_name).call
    end
    obj
  end
end
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