djblets.db.fields.modification_timestamp_field¶

Field for managing modification timestamps for a model.

class ModificationState[source]¶

Bases: object

Modification state for a tracked value.

first_set¶

Whether or not the next setattr() will be the first.

When this is True, we do not consider the next setattr() to be a modification since the field will be set during model initialization.

Type:	bool

modified¶

Whether or not the value has been manually modified.

Type:	bool

__init__()[source]¶

Initialize the state.

static get_attr_name(field_name)[source]¶

Return the attribute name for the state for the named field.

Parameters:	field_name (unicode) – The attribute name of the ModificationTimestampField.
Returns:	The name of the modification state attribute.
Return type:	unicode

class ModificationTrackedValue(field_name, state_name)[source]¶

Bases: object

A descriptor for tracking the modification of a value.

field_name¶

The attribute name of the field on the model.

Type:	unicode

state_name¶

The attribute name of the state on the model.

Type:	unicode

__init__(field_name, state_name)[source]¶

Initialize the descriptor.

Parameters:	field_name (unicode) – The name of the field attribute. state_name (unicode) – The name of the state attribute.

__get__(instance, objtype=None)[source]¶

Return the value.

Parameters:	instance (django.db.models.Model) – The model instance. objtype (type, optional) – The model class.
Returns:	The value.
Return type:	datetime.datetime

__set__(instance, value)[source]¶

Set the value.

This tracks modifications and updates the state if this is not the first call to this method (which occurs during model initialization).

Parameters:	instance (django.db.models.Model) – The instance to set the the value on. value (datetime.datetime) – The value to set.state.first_set:

class ModificationTimestampField(*args, **kwargs)[source]¶

Bases: django.db.models.fields.DateTimeField

A timestamp field that only updates existing objects or when None.

This is a subclass of DateTimeField that only auto-updates the timestamp when updating an existing object or when the value of the field is None. It’s similar to using auto_now=True, but custom timestamp values on new instances will not be replaced.

__init__(*args, **kwargs)[source]¶

Initialize the field.

Parameters:	*args (tuple) – Positional arguments for the field. **kwargs (dict) – Additional keyword arguments for the field.

contribute_to_class(cls, name)[source]¶

Contribute the field attributes to the class.

Parameters:	cls (type) – The model class to contribute the field to. name (unicode) – The name of the field.

pre_save(model_instance, add)[source]¶

Return the value of the field just before saving.

Parameters:	model_instance (django.db.models.Model) – The model instance being saved. add (bool) – Whether this is being saved to the database for the first time.
Returns:	The date/time value being saved.
Return type:	datetime.datetime