I have a model and serializer like this:
models.py
class CalendarEvent(BaseMixin):
title = models.TextField(blank=True, null=True)
class CalendarEventReminder(BaseMixin):
event = models.ForeignKey(CalendarEvent, related_name = 'reminders')
minutes = models.CharField()
class Meta:
managed = False
db_table = 'calendar_event_reminder'
def __str__(self):
return self.minutes
serializer.py
class CalendarEventSerializer(serializers.ModelSerializer):
reminders = serializers.StringRelatedField(many=True)
class Meta:
model = CalendarEvent
fields = ('title', 'reminders')
In my view, I do the following:
def test(request):
#...
event = CalendarEvent.objects.filter(id__in = [930, 935])
serializer = CalendarEventSerializer(event, many = True)
print (serializer.data)
#...
When I open the Debug Toolbar, I see that the database hits reminders table twice for each of the calendar events.
The question is, how this behavior could be optimized.
The most straight-forward way would be prefetching the CalendarEventReminders of the CalendarEvents in your view:
# views.py
def get(request):
event = CalendarEvent.objects.filter(id__in = [930, 935]) \
.prefetch_related('reminders')
# ...
This will prefetch all CalendarEventReminders while getting the CalendarEvents.
Note that this will not trigger a sql join like select_related() would do. We can't use select_related() in this case because we're following the relation backwards. :)
Check out the Django Docs regarding prefetch_related.
Related
I am making a POST api using DRF. In that api, I need only few fields(name, size, customer_name, customer_address), but don't require this fields(status, ordered_time) because these fields I want to save these fields in run time as status='open' and ordered_time=DateTimeField.now()
views.py
class PizzaOrderCustomerView(APIView):
def post(self, request):
orders = request.data.get('orders')
# Create an article from the above data
serializer = ArticleSerializer(data=orders)
if serializer.is_valid(raise_exception=True):
article_saved = serializer.save()
return Response({"success": "Article '{}' created successfully".format(article_saved.name)})
models.py
class PizzaOrder(models.Model):
name = models.CharField(max_length=120)
size = models.CharField(max_length=10, choices=SIZE_CHOICE, default='MEDIUM')
customer_name = models.CharField(max_length=120)
customer_address = models.TextField()
ordered_time = models.DateTimeField(default=timezone.now, editable=False)
status = models.CharField(max_length=20, default='open', editable=False)
serializers.py
class OrderSerializer(serializers.ModelSerializer):
class Meta:
model = PizzaOrder
# fields = '__all__'
read_only_fields = ('status',)
But when I try to create an order, it needed status and ordered_time also. But it should save at the time of creating order automatically.
Suggest a good way to do it.
from rest_framework import viewsets, mixins
class PizzaViewsets(viewsets.ViewSet, mixins.CreateModelMixin):
model = PizzaOrder
serializer_class = OrderSerializer
queryset = model.objects.all(
serializer, it is always good practise to mention all fields instead of
all
class OrderSerializer(serializers.ModelSerializer):
class Meta:
model = PizzaOrder
fields = ('status','ordered_time','name', 'size', 'customer_name', 'customer_address',)
read_only_fields = ('status','ordered_time',)
My problem is that I can not take back any data after filtering.
My search fields are : id name and surname. The two last taken from the Client which is foreign key.
filters.py
class OrderFilter(django_filters.FilterSet):
client__name = django_filters.CharFilter(lookup_expr='icontains')
client__surname = django_filters.CharFilter(lookup_expr='icontains')
class Meta:
model = Order
fields = ['id']
models.py
class Order(models.Model):
client = models.ForeignKey(Client,verbose_name=u'Client')
tables.py
class OrderTable(tables.Table):
#CUSTOM COLUMN EXAMPLE
order_id=tables.Column(verbose_name= 'ID Order',orderable=False,empty_values=())
class Meta:
#define the model
model = Order
exclude=('id')
template_name = 'django_tables2/bootstrap.html'
sequence = ("order_id")
views.py
class OrderListView(SingleTableMixin,FilterView):
table_class = OrderTable
model = Order
template_name='orders/orde_list.html'
filterset_class = OrderFilter
def get_context_data(self, **kwargs):
context = super(OrderListView, self).get_context_data(**kwargs)
##filter the orders of the past 4 months.
last_four_months=date.today() - timedelta(120)
object_list=Order.objects.filter(order_created__gte=last_four_months,ays=1).order_by('-invoice_date')
table=self.table_class(object_list)
RequestConfig(self.request).configure(table)
context['table'] = table
#clear all fields
has_filter = any(field in self.request.GET for field in set(self.filterset_class.get_fields()))
context['has_filter'] = has_filter
return context
I noticed that when I create a custom queryset to fill my table, for ex: object_list=Order.objects.filter(order_created__gte=last_four_months).order_by('-invoice_date') the filtering is not working.
When I put nothing it works properly.
Any idea why this happening?
The issue was that I have not defined that my custom queryset must be inserted in the custom table(tables.py) and more important to be filtered by the custom filter (filters.py).
After doing that the custom queryset filtered correctly.
class OrderAYSListView(LoginRequiredMixin,SingleTableMixin,FilterView):
login_url = '/login/'
table_class = OrderTable2
model = Order
template_name='orders/order_ays_list.html'
filterset_class = OrderFilter
def get_context_data(self, **kwargs):
context = super(OrderAYSListView, self).get_context_data(**kwargs)
##filter the orders of the past 4 months.
last_four_months=date.today() - timedelta(120)
object_list=Order.objects.filter(order_created__gte=last_four_months,ays=1).order_by('-invoice_date')
f = self.filterset_class(self.request.GET, queryset=object_list)
context['filter'] = f
table = self.table_class(f.qs)
RequestConfig(self.request).configure(table)
context['table'] = table
#clear all fields
has_filter = any(field in self.request.GET for field in set(self.filterset_class.get_fields()))
context['has_filter'] = has_filter
return context
I have model
class A(models.Model):
is_enable = models.BooleanField(default=False)
title = models.CharField(max_length=255, blank=True, null=True)
updated_date = models.DateTimeField(auto_now=True)
show_count = models.IntegerField(default=0)
answers_count = models.IntegerField(default=0)
audience = JSONField()
events = JSONField()
rules = JSONField()
message = models.TextField(blank=True)
#property
def conversion(self):
if self.show_count == 0:
return 0.0
return (self.answers_count / self.show_count) * 100
And i have serializer
class ASerializer(serializers.ModelSerializer):
audience = serializers.JSONField()
events = serializers.JSONField()
rules = serializers.JSONField()
class Meta:
model = Trigger
fields = '__all__'
I want to add to response #property conversion` field
and I want to do something like this in serializer
class Meta:
model = Trigger
fields = '__all__' + conversion
I know that i can make something like this
class Meta:
model = Trigger
fields = ('is_enable', 'title' ... 'conversion')
But i want add all fields and conversion field and do this more beautiful
you can use somethig like this:
class ModelMixin:
#classmethod
def _get_model_fields(cls):
all_fields = cls._meta.get_fields()
fields = [i.name for i in all_fields if i.__class__.__name__ not in ['ManyToManyRel', 'GenericRelation', 'ManyToOneRel']]
return fields
#classmethod
def get_serializer_fields(cls):
fields = cls._get_model_fields()
return fields
class A(ModelMixin, models.Model):
...
class ASerializer(ModelSerializer):
custom_field = serializers.JSONField()
class Meta:
model = A
fields = A.get_serializer_fields()
fields.append('cusom_field')
Might still not be as clean as you want it to be, but using <model>._meta.fields you can get all fields of that model, and using the name property of each field you can retrieve the names that refer to them.
As the serializers file is interpreted as python, it supports code execution, meaning you can use all python functionalities when setting properties, including a for loop, which gives us the ability to do this:
fields = (tuple((f.name for f in A._meta.fields)) + ('conversion',))
Needed this for my own model as well and there it seemed to work, so hopefully so does it for you.
You can create a SerializerMethodField in your serializer and later define a method in serializer itself that can call your functions you defined in models using #property
class ASerializer(serializers.ModelSerializer):
audience = serializers.JSONField()
events = serializers.JSONField()
rules = serializers.JSONField()
conversion = serializers.SerializerMethodField()
class Meta:
model = Trigger
fields = '__all__'
def get_conversion(self,obj):
return obj.conversion
This should allow you to keep your code beautiful without modifying much of your code.
How can I pass an argument to a serializers.RelatedField class from views.py. I need to pass language_id to query Language.objects model within that RelatedField.
I am not sure if I took a right approach to this issue. What I want to achieve is to present information about genres associated to a movie from database model about depending on the language. The MovieGenre model has genre ID field which I want to replace with actual Genre name.
My serialiser.py
class GenreField(serializers.RelatedField):
def to_representation(self, value, language_id=1):
genre_name = GenresVideo.objects.get(genre_id=value, language_id=language_id)
return genre_name.name
class MovieGenresSerializer(serializers.ModelSerializer):
genre_id = GenreField(read_only=True)
class Meta:
model = MoviesGenres
As you see, here I query Language.objects with default value but I would like to pass it from views (language_id).
My views.py:
class MovieGenresTestViewSet(viewsets.ModelViewSet):
lookup_field = 'movie'
queryset = MoviesGenres.objects.all()
serializer_class = MovieGenresSerializer
def list(self, request, language_pk):
queryset = MoviesGenres.objects.all()
serializer = MovieGenresSerializer(queryset, many=True)
return Response(serializer.data)
def retrieve(self, request, movie, language_pk):
queryset = MoviesGenres.objects.filter(movie=movie)
serializer = MovieGenresSerializer(queryset, many=True)
return Response(serializer.data)
And my urls.py:
router.register(r'lang', LanguagesViewSet, base_name='lang')
mov_gen = routers.NestedSimpleRouter(router, r'lang', lookup='language')
mov_gen.register(r'mg', MovieGenresTestViewSet, base_name='mg')
url(r'^api/', include(genre_spec.urls))
My models.py
class Languages(models.Model):
name = models.CharField(unique=True, max_length=255)
short_name = models.CharField(unique=True, max_length=4, blank=True, null=True)
active = models.BooleanField(default="")
class Meta:
managed = False
db_table = 'languages'
ordering = ('id',)
class GenresVideo(models.Model):
genre_id = models.IntegerField()
language = models.ForeignKey('Languages')
name = models.CharField(max_length=255, blank=True, null=True)
class Meta:
managed = False
db_table = 'genres_video'
unique_together = (('genre_id', 'language'),)
ordering = ('genre_id',)
class MoviesGenres(models.Model):
movie = models.ForeignKey(Movies)
genre_id = models.IntegerField()
class Meta:
managed = False
db_table = 'movies_genres'
unique_together = (('movie', 'genre_id'),)
Through the urls routes, I can get a correct response from API including the language_id. I just need to pass it to the view somehow.
Thanks a lot for help!
I'll try to answer to your first question, with the easiest implementation possible: SerializerMethodField. Because we will get the language id via the context passed to the serializer, we should either generate the context for the serializer, or let the framework do that for us.
Now to the problem at hand: you aren't filtering the queryset (MoviesGenres) by language per se. Thus, we can avoid overwriting the list and retrieve methods. Nevertheless, the router mechanism will inject in kwargs for the view method the language_pk parameter - that's the parameter that we will retrieve from within the serializer context:
class MovieGenresSerializer(serializers.ModelSerializer):
genre = searializers.SerializerMethodField()
class Meta:
model = MoviesGenres
def get_genre(self, instance):
# get the language id from the view kwargs
language_id = self.context['view'].kwargs['language_pk']
# get the genre
try:
genre_name = GenresVideo.objects.get(genre_id=instance.genre_id, language_id=language_id).name
except GenresVideo.DoesNotExist:
genre_name = None
# return the formatted output
return genre_name
class MovieGenresTestViewSet(viewsets.ModelViewSet):
lookup_field = 'movie'
queryset = MoviesGenres.objects.all()
serializer_class = MovieGenresSerializer
I am trying to filter a field on a ModelForm. I am subclassing the generic CreateView for my view. I found many references to my problem on the web, but the solutions do not seem to work (for me at least) with Django 1.3's class-based views.
Here are my models:
#models.py
class Subscriber(models.Model):
user = models.ForeignKey(User)
subscriber_list = models.ManyToManyField('SubscriberList')
....
class SubscriberList(models.Model):
user = models.ForeignKey(User)
name = models.CharField(max_length=70)
....
Here is my view:
#views.py
class SubscriberCreateView(AuthCreateView):
model = Subscriber
template_name = "forms/app.html"
form_class = SubscriberForm
success_url = "/app/subscribers/"
def form_valid(self, form):
self.object = form.save(commit=False)
self.object.user = self.request.user
return super(SubscriberCreateView, self).form_valid(form)
Here is my original form for adding a Subscriber, with no filter:
#forms.py
class SubscriberForm(ModelForm):
class Meta:
model = Subscriber
exclude = ('user', 'facebook_id', 'twitter_id')
Here is my modified form, attempting to filter, but doesn't work:
#forms.py
class SubscriberForm(ModelForm):
class Meta:
model = Subscriber
exclude = ('user', 'facebook_id', 'twitter_id')
def __init__(self, user, **kwargs):
super(SubscriberForm, self).__init__(**kwargs)
self.fields['subscriber_list'].queryset = SubscriberList.objects.filter(user=user)
If I change this modified form as so:
def __init__(self, user=None, **kwargs)
It works - It brings me NO subscriber lists. But any way I try to pass the request user, I invariably get a a name "request" or name "self" not defined error.
So, how can I modify my code to filter subscriber_list by the request.user, and still use Django 1.3's CreateView.
I see you've been posting this question in various places.. and the way I found that is because I was trying to figure out the same thing. I think I just got it working, and here's what I did. I overwrote get_form() from FormMixin to filter a specific form fields queryset:
class MyCreateView(CreateView):
def get_form(self, form_class):
form = super(MyCreateView,self).get_form(form_class) #instantiate using parent
form.fields['my_list'].queryset = MyObject.objects.filter(user=self.request.user)
return form