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module ActiveRecord
# Track unsaved attribute changes.
#
# A newly instantiated object is unchanged:
# person = Person.find_by_name('uncle bob')
# person.changed? # => false
#
# Change the name:
# person.name = 'Bob'
# person.changed? # => true
# person.name_changed? # => true
# person.name_was # => 'uncle bob'
# person.name_change # => ['uncle bob', 'Bob']
# person.name = 'Bill'
# person.name_change # => ['uncle bob', 'Bill']
#
# Save the changes:
# person.save
# person.changed? # => false
# person.name_changed? # => false
#
# Assigning the same value leaves the attribute unchanged:
# person.name = 'Bill'
# person.name_changed? # => false
# person.name_change # => nil
#
# Which attributes have changed?
# person.name = 'bob'
# person.changed # => ['name']
# person.changes # => { 'name' => ['Bill', 'bob'] }
#
# Before modifying an attribute in-place:
# person.name_will_change!
# person.name << 'by'
# person.name_change # => ['uncle bob', 'uncle bobby']
module Dirty
def self.included(base)
base.attribute_method_suffix '_changed?', '_change', '_will_change!', '_was'
base.alias_method_chain :write_attribute, :dirty
base.alias_method_chain :save, :dirty
base.alias_method_chain :save!, :dirty
base.alias_method_chain :update, :dirty
base.alias_method_chain :reload, :dirty
base.superclass_delegating_accessor :partial_updates
base.partial_updates = true
end
# Do any attributes have unsaved changes?
# person.changed? # => false
# person.name = 'bob'
# person.changed? # => true
def changed?
!changed_attributes.empty?
end
# List of attributes with unsaved changes.
# person.changed # => []
# person.name = 'bob'
# person.changed # => ['name']
def changed
changed_attributes.keys
end
# Map of changed attrs => [original value, new value].
# person.changes # => {}
# person.name = 'bob'
# person.changes # => { 'name' => ['bill', 'bob'] }
def changes
changed.inject({}) { |h, attr| h[attr] = attribute_change(attr); h }
end
# Attempts to +save+ the record and clears changed attributes if successful.
def save_with_dirty(*args) #:nodoc:
if status = save_without_dirty(*args)
changed_attributes.clear
end
status
end
# Attempts to <tt>save!</tt> the record and clears changed attributes if successful.
def save_with_dirty!(*args) #:nodoc:
status = save_without_dirty!(*args)
changed_attributes.clear
status
end
# <tt>reload</tt> the record and clears changed attributes.
def reload_with_dirty(*args) #:nodoc:
record = reload_without_dirty(*args)
changed_attributes.clear
record
end
private
# Map of change <tt>attr => original value</tt>.
def changed_attributes
@changed_attributes ||= {}
end
# Handle <tt>*_changed?</tt> for +method_missing+.
def attribute_changed?(attr)
changed_attributes.include?(attr)
end
# Handle <tt>*_change</tt> for +method_missing+.
def attribute_change(attr)
[changed_attributes[attr], __send__(attr)] if attribute_changed?(attr)
end
# Handle <tt>*_was</tt> for +method_missing+.
def attribute_was(attr)
attribute_changed?(attr) ? changed_attributes[attr] : __send__(attr)
end
# Handle <tt>*_will_change!</tt> for +method_missing+.
def attribute_will_change!(attr)
changed_attributes[attr] = clone_attribute_value(:read_attribute, attr)
end
# Wrap write_attribute to remember original attribute value.
def write_attribute_with_dirty(attr, value)
attr = attr.to_s
# The attribute already has an unsaved change.
if changed_attributes.include?(attr)
old = changed_attributes[attr]
changed_attributes.delete(attr) unless field_changed?(attr, old, value)
else
old = clone_attribute_value(:read_attribute, attr)
changed_attributes[attr] = old if field_changed?(attr, old, value)
end
# Carry on.
write_attribute_without_dirty(attr, value)
end
def update_with_dirty
if partial_updates?
# Serialized attributes should always be written in case they've been
# changed in place.
update_without_dirty(changed | self.class.serialized_attributes.keys)
else
update_without_dirty
end
end
def field_changed?(attr, old, value)
if column = column_for_attribute(attr)
if column.type == :integer && column.null && (old.nil? || old == 0)
# For nullable integer columns, NULL gets stored in database for blank (i.e. '') values.
# Hence we don't record it as a change if the value changes from nil to ''.
# If an old value of 0 is set to '' we want this to get changed to nil as otherwise it'll
# be typecast back to 0 (''.to_i => 0)
value = nil if value.blank?
else
value = column.type_cast(value)
end
end
old != value
end
end
end
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