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Contents
module TemporalTables
# 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)
module HistoryHook
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
# Returns a scope for the list of all history records for this
# particular object.
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
end
end
ActiveRecord::Base.send :include, TemporalTables::HistoryHook
Version data entries
8 entries across 8 versions & 1 rubygems