ActiveRecord::AttributeMethods::Dirty

    # File lib/active_record/attribute_methods/dirty.rb, line 90
90:       def clone_with_time_zone_conversion_attribute?(attr, old)
91:         old.class.name == "Time" && time_zone_aware_attributes && !skip_time_zone_conversion_for_attributes.include?(attr.to_sym)
92:       end

    # File lib/active_record/attribute_methods/dirty.rb, line 74
74:       def field_changed?(attr, old, value)
75:         if column = column_for_attribute(attr)
76:           if column.number? && column.null && (old.nil? || old == 0) && value.blank?
77:             # For nullable numeric columns, NULL gets stored in database for blank (i.e. '') values.
78:             # Hence we don't record it as a change if the value changes from nil to ''.
79:             # If an old value of 0 is set to '' we want this to get changed to nil as otherwise it'll
80:             # be typecast back to 0 (''.to_i => 0)
81:             value = nil
82:           else
83:             value = column.type_cast(value)
84:           end
85:         end
86: 
87:         old != value
88:       end

    # File lib/active_record/attribute_methods/dirty.rb, line 64
64:       def update(*)
65:         if partial_updates?
66:           # Serialized attributes should always be written in case they've been
67:           # changed in place.
68:           super(changed | (attributes.keys & self.class.serialized_attributes.keys))
69:         else
70:           super
71:         end
72:       end

    # File lib/active_record/attribute_methods/dirty.rb, line 46
46:       def write_attribute(attr, value)
47:         attr = attr.to_s
48: 
49:         # The attribute already has an unsaved change.
50:         if attribute_changed?(attr)
51:           old = @changed_attributes[attr]
52:           @changed_attributes.delete(attr) unless field_changed?(attr, old, value)
53:         else
54:           old = clone_attribute_value(:read_attribute, attr)
55:           # Save Time objects as TimeWithZone if time_zone_aware_attributes == true
56:           old = old.in_time_zone if clone_with_time_zone_conversion_attribute?(attr, old)
57:           @changed_attributes[attr] = old if field_changed?(attr, old, value)
58:         end
59: 
60:         # Carry on.
61:         super(attr, value)
62:       end