post.rb

class Post < ActiveRecord::Base
  class << self
    def get_column(column)
      columns.select do |column_|
        column_.name == column.to_s
      end[0]
    end

    def any(what)
      out = all
      what.each.with_index(1) do |(key_, value_), index_|
        key_ = get_column(key_) || raise(ActiveRecord::PreparedStatementInvalid, "no column #{key_}")
        out  = out.where(<<-SQL.strip_heredoc.strip).bind([key_, value_])
          $#{index_} = ANY("#{table_name}"."#{key_.name}")
        SQL
      end
    out
    end
  end
end