django-manager-utils 0.3.4

Model manager utilities for Django

[](https://travis-ci.org/ambitioninc/django-manager-utils)
django-manager-utils
=====================

Additional utilities for Django model managers.

## A Brief Overview
Django manager utils allows a user to perform various functions not natively supported by Django's model managers. To use the manager in your Django models, do:

from manager_utils import ManagerUtilsManager

class MyModel(Model):
objects = ManagerUtilsManager()

If you want to extend an existing manager to use the manager utils, include mixin provided first (since it overrides the get_queryset function) as follows:

from manager_utils import ManagerUtilsMixin

class MyManager(ManagerUtilsMixin, Manager):
pass

An overview of each util is below with links to more in-depth documentation and examples for each function.

- [single](#single): Grabs a single element from table and verifies it is the only element.
- [get_or_none](#get_or_none): Performs a get on a queryset and returns None if the object does not exist.
- [upsert](#upsert): Performs an upsert (update or insert) to a model.
- [bulk_update](#bulk_update): Bulk updates a list of models and the fields that have been updated.
- [id_dict](#id_dict): Returns a dictionary of objects keyed on their ID.
- [post_bulk_operation](#post_bulk_operation): A signal that is fired when a bulk operation happens.

## single()<a name="single"></a>
Assumes that the model only has one element in the table or queryset and returns that value. If the table has more than one or no value, an exception is raised.

**Returns**: The only model object in the queryset.

**Raises**: DoesNotExist error when the object does not exist or a MultipleObjectsReturned error when there is more than one object.

**Examples**:

TestModel.objects.create(int_field=1)
model_obj = TestModel.objects.single()
print model_obj.int_field
1

## get_or_none(\*\*query_params)<a name="get_or_none"></a>
Get an object or return None if it doesn't exist.

**Args**:
- \*\*query_params: The query parameters used in the lookup.

**Returns**: A model object if one exists with the query params, None otherwise.

**Examples**:

model_obj = TestModel.objects.get_or_none(int_field=1)
print model_obj
None

TestModel.objects.create(int_field=1)
model_obj = TestModel.objects.get_or_none(int_field=1)
print model_obj.int_field
1

## upsert(defaults=None, updates=None, \*\*kwargs)<a name="upsert"></a>
Performs an update on an object or an insert if the object does not exist.

**Args**:
- defaults: These values are set when the object is inserted, but are irrelevant when the object already exists. This field should only be used when values only need to be set during creation.
- updates: These values are updated when the object is updated. They also override any values provided in the defaults when inserting the object.
- \*\*kwargs: These values provide the arguments used when checking for the existence of the object. They are used in a similar manner to Django's get_or_create function and are set in a created object.

**Returns**: A tuple of the upserted object and a Boolean that is True if it was created (False otherwise)

**Examples**:

# Upsert a test model with an int value of 1. Use default values that will be given to it when created
model_obj, created = TestModel.objects.upsert(int_field=1, defaults={'float_field': 2.0})
print created
True
print model_obj.int_field, model_obj.float_field
1, 2.0

# Do an upsert on that same model with different default fields. Since it already exists, the defaults
# are not used
model_obj, created = TestModel.objects.upsert(int_field=1, defaults={'float_field': 3.0})
print created
False
print model_obj.int_field, model_obj.float_field
1, 2.0

# In order to update the float field in an existing object, use the updates dictionary
model_obj, created = TestModel.objects.upsert(int_field=1, updates={'float_field': 3.0})
print created
False
print model_obj.int_field, model_obj.float_field
1, 3.0

# You can use updates on a newly created object that will also be used as initial values.
model_obj, created = TestModel.objects.upsert(int_field=2, updates={'float_field': 4.0})
print created
True
print model_obj.int_field, model_obj.float_field
2, 4.0

## bulk_update(model_objs, fields_to_update)<a name="bulk_update"></a>
Performs an bulk update on an list of objects. Any fields listed in the fields_to_update array will be updated in the database.

**Args**:
- model_objs: A list of model objects that are already stored in the database.
- fields_to_update: A list of fields to update in the models. Only these fields will be updated in the database. The 'id' field is included by default.

**Examples**:

# Create a couple test models
model_obj1 = TestModel.objects.create(int_field=1, float_field=2.0, char_field='Hi')
model_obj2 = TestModel.objects.create(int_field=3, float_field=4.0, char_field='Hello')

# Change their fields and do a bulk update
model_obj1.int_field = 10
model_obj1.float_field = 20.0
model_obj2.int_field = 30
model_obj2.float_field = 40.0
TestModel.objects.bulk_update([model_obj1, model_obj2], ['int_field', 'float_field'])

# Reload the models and view their changes
model_obj1 = TestModel.objects.get(id=model_obj1.id)
print model_obj1.int_field, model_obj1.float_field
10, 20.0

model_obj2 = TestModel.objects.get(id=model_obj2.id)
print model_obj2.int_field, model_obj2.float_field
10, 20.0

## id_dict()<a name="id_dict"></a>
Returns a dictionary of the model objects keyed on their ID.

**Examples**

TestModel.objects.create(int_field=1)
TestModel.objects.create(int_field=2)

print TestModel.objects.id_dict()
{1: <TestModel: TestModel object>, 2: <TestModel: TestModel object>}

print TestModel.objects.filter(int_field=2).id_dict()
{2: <TestModel: TestModel object>}

## post_bulk_operation(providing_args=['model'])<a name="post_bulk_operation"></a>
A signal that is emitted at the end of a bulk operation. The current bulk operations are Django's update and bulk_create methods and this package's bulk_update method. The signal provides the model that was updated.

**Examples**

from manager_utils import post_bulk_operation

def signal_handler(self, *args, **kwargs):
print kwargs['model']

post_bulk_operation.connect(signal_handler)

TestModel.objects.all().update(int_field=1)
<type 'TestModel'>

## License
MIT License (See the LICENSE file included in this repository)