Module: ChronoModel::TimeMachine

Extended by:
ActiveSupport::Concern
Includes:
Patches::AsOfTimeHolder
Defined in:
lib/chrono_model/time_machine.rb,
lib/chrono_model/time_machine/timeline.rb,
lib/chrono_model/time_machine/time_query.rb,
lib/chrono_model/time_machine/history_model.rb

Defined Under Namespace

Modules: ClassMethods, HistoryModel, TimeQuery, Timeline

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Patches::AsOfTimeHolder

#as_of_time, #as_of_time!

Class Method Details

.define_history_model_for(model) ⇒ Object 



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# File 'lib/chrono_model/time_machine.rb', line 75

def self.define_history_model_for(model)
  history = Class.new(model) do
    include ChronoModel::TimeMachine::HistoryModel
  end

  model.singleton_class.instance_eval do
    define_method(:history) { history }
  end

  model.const_set :History, history
end

Instance Method Details

#as_of(time) ⇒ Object

Returns a read-only representation of this record as it was time ago. Returns nil if no record is found.



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# File 'lib/chrono_model/time_machine.rb', line 123

def as_of(time)
  _as_of(time).first
end

#as_of!(time) ⇒ Object

Returns a read-only representation of this record as it was time ago. Raises ActiveRecord::RecordNotFound if no record is found.



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# File 'lib/chrono_model/time_machine.rb', line 130

def as_of!(time)
  _as_of(time).first!
end

#changes_against(ref) ⇒ Object

Returns the differences between this record and an arbitrary reference record. The changes representation is an hash keyed by attribute whose values are arrays containing previous and current attributes values - the same format used by ActiveModel::Dirty.



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# File 'lib/chrono_model/time_machine.rb', line 226

def changes_against(ref)
  self.class.attribute_names_for_history_changes.inject({}) do |changes, attr|
    old = ref.public_send(attr)
    new = public_send(attr)

    changes.tap do |c|
      changed =
        if old.respond_to?(:history_eql?)
          !old.history_eql?(new)
        else
          old != new
        end

      c[attr] = [old, new] if changed
    end
  end
end

#current_version ⇒ Object

Returns the current history version



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# File 'lib/chrono_model/time_machine.rb', line 205

def current_version
  if historical?
    self.class.find(id)
  else
    self
  end
end

#destroy ⇒ Object

Inhibit destroy of historical records

Raises:

  • (ActiveRecord::ReadOnlyRecord) 


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# File 'lib/chrono_model/time_machine.rb', line 164

def destroy
  raise ActiveRecord::ReadOnlyRecord, 'Cannot delete historical records' if historical?

  super
end

#historical? ⇒ Boolean

Returns a boolean indicating whether this record is an history entry.

Returns:

  • (Boolean) 


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# File 'lib/chrono_model/time_machine.rb', line 158

def historical?
  as_of_time.present?
end

#history ⇒ Object

Return the complete read-only history of this instance.



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# File 'lib/chrono_model/time_machine.rb', line 145

def history
  self.class.history.chronological.of(self)
end

#last_changes ⇒ Object

Returns the differences between this entry and the previous history one. See: changes_against.



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# File 'lib/chrono_model/time_machine.rb', line 216

def last_changes
  pred = self.pred
  changes_against(pred) if pred
end

#pred(options = {}) ⇒ Object

Returns the previous record in the history, or nil if this is the only recorded entry.



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# File 'lib/chrono_model/time_machine.rb', line 173

def pred(options = {})
  if self.class.timeline_associations.empty?
    history.reverse_order.second
  else
    return nil unless (ts = pred_timestamp(options))

    order_clause = Arel.sql %[ LOWER(#{options[:table] || self.class.quoted_table_name}."validity") DESC ]

    self.class.as_of(ts).order(order_clause).find(options[:id] || id)
  end
end

#pred_timestamp(options = {}) ⇒ Object

Returns the previous timestamp in this record’s timeline. Includes temporal associations.



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# File 'lib/chrono_model/time_machine.rb', line 188

def pred_timestamp(options = {})
  if historical?
    options[:before] ||= as_of_time
    timeline(options.merge(limit: 1, reverse: true)).first
  else
    timeline(options.merge(limit: 2, reverse: true)).second
  end
end

#succ ⇒ Object

This is a current record, so its next instance is always nil.



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# File 'lib/chrono_model/time_machine.rb', line 199

def succ
  nil
end

#timeline(options = {}) ⇒ Object

Returns an Array of timestamps for which this instance has an history record. Takes temporal associations into account.



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# File 'lib/chrono_model/time_machine.rb', line 152

def timeline(options = {})
  self.class.history.timeline(self, options)
end