Module: MultirowCounter::Extension

Defined in:
lib/multirow_counter/extension.rb

Instance Method Summary collapse

Instance Method Details

#multirow_counter(counter_name, options) ⇒ Object 



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# File 'lib/multirow_counter/extension.rb', line 3

def multirow_counter(counter_name, options)
  num_rows = options[:rows] || raise(ArgumentError, "You need to specify how many rows will be used eg. :rows => 3")
  class_name = self.name

  assoc = class_name.foreign_key
  table_name = [class_name, counter_name.to_s.camelize].join.tableize

  # define getter method
  getter = lambda do
    ivar_name = "@#{counter_name}"
    if x = instance_variable_get(ivar_name)
      return x
    else
      val = ActiveRecord::Base.connection.select_value <<-SQL
        SELECT IFNULL(SUM(value),0) FROM #{table_name} WHERE #{assoc}=#{self.id}
      SQL
      instance_variable_set(ivar_name, val.to_i)
    end
  end

  define_method(counter_name, &getter)
  define_method("multirow_counter_#{counter_name}", &getter)

  # define increment method
  define_method("new_#{counter_name}!") do |incr = 1|
    ivar_name = "@#{counter_name}"
    if x = instance_variable_get(ivar_name)
      instance_variable_set(ivar_name, x + incr)
    end

    randomly_selected_counter_row = rand(num_rows) + 1

    num_changed = ActiveRecord::Base.connection.update <<-SQL
      UPDATE #{table_name} SET value=value+#{Integer(incr)}
        WHERE #{assoc}=#{self.id} AND counter_id=#{randomly_selected_counter_row}
    SQL

    if num_changed == 0 # row doesn't exist. We create it instead.
      ActiveRecord::Base.connection.execute <<-SQL
        INSERT INTO #{table_name} (#{assoc}, counter_id, value)
          VALUES (#{self.id}, #{randomly_selected_counter_row}, #{Integer(incr)})
          ON DUPLICATE KEY UPDATE value=value+#{Integer(incr)};
      SQL
    end
  end

  define_method("reload_with_#{counter_name}_reset") do
    instance_variable_set("@#{counter_name}", nil)
    send("reload_without_#{counter_name}_reset")
  end

  alias_method_chain :reload, "#{counter_name}_reset".to_sym
end