Module: TemporalTables::HistoryHook

Defined in:
lib/temporal_tables/history_hook.rb

Overview

This hooks in a “history” method to ActiveRecord::Base which will return the class’s History class. The history class extends the original class, but runs against the history table to provide temporal results.

class Person < ActiveRecord::Base
  attr_accessible :name
end

Person         #=> Person(id: integer, name: string)
Person.history #=> PersonHistory(history_id: integer, id: integer, name: string, eff_from: datetime, eff_to: datetime)

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(base) ⇒ Object 



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# File 'lib/temporal_tables/history_hook.rb', line 13

def self.included(base)
	base.class_eval do
		# Return this class's history class.
		# If it doesn't exist yet, create and initialize it, as well
		# as all dependent classes (through associations).
		def self.history
			raise "Can't view history of history" if name =~ /History$/

			history_class = "#{name}History"
			history_class.constantize
		rescue NameError
			# If the history class doesn't exist yet, create it
			new_class = Class.new(self) do
				include TemporalTables::TemporalClass
			end
			segments = history_class.split("::")
			object_class = segments[0...-1].inject(Object) { |o, s| o.const_get(s) }
			object_class.const_set segments.last, new_class

			# Traverse associations and make sure they have
			# history classes too.
			history_class.constantize.temporalize_associations!
			history_class.constantize
		end	
	end
end

Instance Method Details

#history ⇒ Object

Returns a scope for the list of all history records for this particular object.



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# File 'lib/temporal_tables/history_hook.rb', line 42

def history
	clazz = is_a?(TemporalTables::TemporalClass) ? self.class : self.class.history
	oid = is_a?(TemporalTables::TemporalClass) ? orig_class.primary_key : self.class.primary_key
	clazz.unscoped.where(id: attributes[oid]).order(:eff_from)
end