field_alias.rb

module FieldAlias
  
  #列挙タイプのエイリアス定義
  #ex define_alias_enum(:original, :alias, {0 => "NG", 1 => "OK", nil => "-", other: "不明"})
  ###from
  #def receipt_status
  #  case receipt
  #  when 0
  #    "-"
  #  when 1
  #    "必要"
  #  when 2
  #    "不要"
  #  else
  #    "不明な値"
  #  end
  #end
  ###to
  #define_alias_enum(:receipt, :receipt_status, {0 => "-", 1 => "必要", 2 => "不要", other: "不明な値"})
  def define_alias_enum(method_name, alias_name, args)
    define_method alias_name do
      value = self.send method_name
      if args.has_key? value
        args[value]
      elsif args.has_key? :other
        args[:other]
      end
    end
  end
  
  #nil値を別の値にするタイプのエイリアス定義
  #ex1 define_alias_nil(:original, :alias, "-")
  #ex2 define_alias_nil(:original, :alias, "-") {|v| v.upcase }
  def define_alias_nil(method_name, alias_name, nilvalue, &block)
    define_method alias_name do
      value = self.send(method_name)
      if value
        block_given? ? yield(value) : value
      else
        nilvalue
      end
    end
  end

end