djblets.db.fields.modification_timestamp_field¶

Field for managing modification timestamps for a model.

class ModificationState¶

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__()¶

Initialize the state.

static get_attr_name(field_name)¶

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)¶

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)¶

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)¶

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)¶

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)¶

Bases: 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)¶

Initialize the field.

Parameters:

• *args (tuple) – Positional arguments for the field.

• **kwargs (dict) – Additional keyword arguments for the field.

contribute_to_class(cls, name)¶

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)¶

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