mirror of
https://github.com/scrapy/scrapy.git
synced 2025-02-24 23:23:47 +00:00
91 lines
2.4 KiB
ReStructuredText
91 lines
2.4 KiB
ReStructuredText
.. _topics-djangoitem:
|
|
|
|
.. module:: scrapy.contrib_exp.djangoitem
|
|
|
|
==========
|
|
DjangoItem
|
|
==========
|
|
|
|
:class:`DjangoItem` is a class of item that gets its fields definition from a
|
|
Django model, you simply create a :class:`DjangoItem` and specify what Django
|
|
model it relates to.
|
|
|
|
Besides of getting the model fields defined on your item, :class:`DjangoItem`
|
|
provides a method to create and populate a Django model instance with the item
|
|
data.
|
|
|
|
Using DjangoItem
|
|
================
|
|
|
|
:class:`DjangoItem` works much like ModelForms in Django, you create a subclass
|
|
and define its ``django_model`` atribute to ve a valid Django model. With this
|
|
you will get an item with a field for each Django model field.
|
|
|
|
In addition, you can define fields that aren't present in the model and even
|
|
override fields that are present in the model defining them in the item.
|
|
|
|
Let's see some examples:
|
|
|
|
Django model for the examples::
|
|
|
|
class Person(models.Model):
|
|
name = models.CharField(max_length=255)
|
|
age = models.IntegerField()
|
|
|
|
Defining a basic :class:`DjangoItem`::
|
|
|
|
class PersonItem(DjangoItem):
|
|
django_model = Person
|
|
|
|
:class:`DjangoItem` work just like :class:`~scrapy.item.Item`::
|
|
|
|
p = PersonItem()
|
|
p['name'] = 'John'
|
|
p['age'] = '22'
|
|
|
|
To obtain the Django model from the item, we call the extra method
|
|
:meth:`~DjangoItem.save` of the :class:`DjangoItem`::
|
|
|
|
>>> person = p.save()
|
|
>>> person.name
|
|
'John'
|
|
>>> person.age
|
|
'22'
|
|
>>> person.id
|
|
1
|
|
|
|
As you see the model is already saved when we call :meth:`~DjangoItem.save`, we
|
|
can prevent this by calling it with ``commit=False``. We can use
|
|
``commit=False`` in :meth:`~DjangoItem.save` method to obtain an unsaved model::
|
|
|
|
>>> person = p.save(commit=False)
|
|
>>> person.name
|
|
'John'
|
|
>>> person.age
|
|
'22'
|
|
>>> person.id
|
|
None
|
|
|
|
As said before, we can add other fields to the item::
|
|
|
|
class PersonItem(DjangoItem):
|
|
django_model = Person
|
|
sex = Field()
|
|
|
|
p = PersonItem()
|
|
p['name'] = 'John'
|
|
p['age'] = '22'
|
|
p['sex'] = 'M'
|
|
|
|
.. note:: fields added to the item won't be taken into account when doing a
|
|
:meth:`~DjangoItem.save`
|
|
|
|
And we can override the fields of the model with your own::
|
|
|
|
class PersonItem(DjangoItem):
|
|
django_model = Person
|
|
name = Field(default='No Name')
|
|
|
|
This is usefull to provide properties to the field, like a default or any other
|
|
property that your project uses.
|