I want to serialize a QuerySet that contains an extra statement:
region_list = Region.objects.extra(select={ 'selected': 'case when id = %s then 1 else 0 end' % (new_region.id)}).all()
I use the statement below to serialize
return HttpResponse(serializers.serialize('json', region_list), mimetype='application/json')
But when I obtain the json results in the browser, only the fields of the Region model appears, the selected field dissapear.
How can I fix that?
One slightly longwinded solution would be to to dump the objects to JSON via django-piston's JSONEmitter class. When you register your Region model with piston, you can say what fields to include, and mention 'selected' there, and then use your annotation to make sure that the queryset used in the piston handler contains all the info you want.
Or just look at how piston does it and, if you don't want all of piston, just mimic the bits you do.
Related
How can I resolve a resource_uri during a Tastypie hydrate call?
I am passing the following data object to a Tastypie resource:
{
'date': u'2013-10-31 15:06',
'visitor': u'/visitorlog/api/v1/person/33/',
'purpose': u'Testing'
}
I would like to take the visitor and pull the entire record in a hydrate function, which populates a field with some extra information.
I am currently doing this by splitting out the id and performing a search:
def hydrate_meta(self, bundle):
'''
This will populate the `meta` field with a snapshot of the employee record, if the `empid` is set. This is done so if the employee record changes we retain certain information at the time of the visit.
'''
split_id = bundle.data['visitor'].split('/')
# the id of `visitor` is in `split_id[-2]
# get the record of this visitor from the Django model
person_record = Person.objects.get(pk = split_id[-2])
# ... snipped ... create the `meta_value` object
bundle.data['meta'] = meta_values
return bundle
This is working, but calling split on the resource_uri does not seem the most elegant way to do this.
Is there more effective way to pull a record given a resource_uri?
Resource.get_via_uri(url) (doc) might come in handy.
I have a Django Tastypie API set up.
I would like to query the database for the count of objects that match a name.
Is this possible on an existing model resource, or do I need to set up a new resource to handle this specific case? (This data is usually returned in the metadata part of the result? Is there an option just to return that from the paramaters?)
So if my url is usually like this:
http://127.0.0.1:8000/api/v1/library/?name__icontains=ABC
Can I add a parameter or change the url so that it only returns the metadata (I only want the number of libraries returned that have a name containing "ABC") rather than all the objects?
You can pass in a get param:
http://127.0.0.1:8000/api/v1/library/?name__icontains=ABC&meta_only=true
and add this method to your resource:
def alter_list_data_to_serialize(self, request, data):
if request.GET.get('meta_only'):
return {'meta': data['meta']}
return data
documentation : http://django-tastypie.readthedocs.org/en/latest/resources.html#alter-list-data-to-serialize
I'm trying to render a form with a combo that shows related entities. Therefore I'm using a ModelChoiceField.
This approach works well, until I needed to limit which entities to show. If I use a simple query expression it also works well, but things break if I use a raw SQL query.
So my code that works, sets the queryset to a filter expression.
class ReservationForm(forms.Form):
location_time_slot = ModelChoiceField(queryset=LocationTimeSlot.objects.all(), empty_label="Select your prefered time")
def __init__(self,*args,**kwargs):
city_id = kwargs.pop("city_id") # client is the parameter passed from views.py
super(ReservationForm, self).__init__(*args,**kwargs)
# TODO: move this to a manager
self.fields['location_time_slot'].queryset = LocationTimeSlot.objects.filter(city__id = city_id )
BUT, if I change that to a raw query I start having problems. Code that does not work:
class ReservationForm(forms.Form):
location_time_slot = ModelChoiceField(queryset=LocationTimeSlot.objects.all(), empty_label="Select your prefered time")
def __init__(self,*args,**kwargs):
city_id = kwargs.pop("city_id") # client is the parameter passed from views.py
super(ReservationForm, self).__init__(*args,**kwargs)
# TODO: move this to a manager
query = """SELECT ts.id, ts.datetime_to, ts.datetime_from, ts.available_reserves, l.name, l.'order'
FROM reservations_locationtimeslot AS ts
INNER JOIN reservations_location AS l ON l.id = ts.location_id
WHERE l.city_id = %s
AND ts.available_reserves > 0
AND ts.datetime_from > datetime() """
time_slots = LocationTimeSlot.objects.raw(query, [city_id])
self.fields['location_time_slot'].queryset = time_slots
The first error I get when trying to render the widget is: 'RawQuerySet' object has no attribute 'all'
I could solve that one thanks to one of the commets in enter link description here, by doing:
time_slots.all = time_slots.__iter__ # Dummy fix to allow default form rendering with raw SQL
But now I'm getting something similar when posting the form:
'RawQuerySet' object has no attribute 'get'
Is there a proper way to prepare a RawQuerySet to be used by ModelChoiceField?
Thanks!
Are you sure you actually need a raw query there? Just looking at that query, I can't see any reason you can't just do it with filter(location__city=city_id, available_reserves__gte=0, datetime_from__gt=datetime.datetime.now()).
Raw query sets are missing a number of methods that are defined on conventional query sets, so just dropping them in place isn't likely to work without writing your own definitions for all those methods.
I temporarily fixed the problem adding the missing methods.
The way I'm currently using the ModelChoiceField I only needed to add the all() and get() methods, but in different scenarios you might need to add some other methods as well. Also this is not a perfect solution because:
1) Defining the get method this way migth produce incorrect results. I think the get() method is used to validate that the selected option is within the options returned by all(). The way I temporarily implemented it only validates that the id exists in the table.
2) I guess the get method is less performant specified this way.
If anyone can think of a better solution, please let me know.
So my temporary solution:
class LocationTimeSlotManager(models.Manager):
def availableSlots(self, city_id):
query = """SELECT ts.id, ts.datetime_to, ts.datetime_from, ts.available_reserves, l.name, l.'order'
FROM reservations_locationtimeslot AS ts
.....
.....
MORE SQL """
time_slots = LocationTimeSlot.objects.raw(query, [city_id])
# Dummy fix to allow default form rendering with raw SQL
time_slots.all = time_slots.__iter__
time_slots.get = LocationTimeSlot.objects.get
return time_slots
I was wondering what is the correct approach,
Do I create HiddenInput fields in my ModelForm and from the
View I pass in the primaryKey for the models I am about to edit into
the hiddenInput fields and then grab those hiddenInput fields from
the AJAX script to use it like this?
item.load(
"/bookmark/save/" + hidden_input_field_1,
null,
function () {
$("#save-form").submit(bookmark_save);
}
);
Or is there is some more clever way of doing it and I have no idea?
Thanks
It depends upon how you want to implement.
The basic idea is to edit 1. you need to get the existing instance, 2. Save provided information into this object.
For #1 you can do it multiple ways, like passing ID or any other primary key like attribute in url like http://myserver/edit_object/1 , Or pass ID as hidden input then you have to do it through templates.
For #2, I think you would already know this. Do something like
inst = MyModel.objects.get(id=input_id) # input_id taken as per #1
myform = MyForm(request.POST, instance=inst)
if myform.is_valid():
saved_inst = myform.save()
I just asked in the django IRC room and it says:
since js isn't processed by the django template engine, this is not
possible.
Hence the id or the object passed in from django view can't be accessed within AJAX script.
I've been using the built-in Django comments system which has been working great. On a particular page I need to list the latest X comments which I've just been fetching with:
latest_comments =
Comment.objects.filter(is_public=True, is_removed=False)
.order_by('submit_date').reverse()[:5]
However I've now introduced a Boolean field 'published' into the parent object of the comments, and I want to include that in the query above. I've tried using the content_type and object_pk fields but I'm not really getting anywhere. Normally you'd do something like:
Comment.objects.filter(blogPost__published=True)
But as it is not stored like that I am not sure how to proceed.
posts_ids = BlogPost.objects.filter(is_published=True).values_list('id', flat=True) #return [3,4,5,...]
ctype = ContentType.objects.get_for_model(BlogPost)
latest_comments = Comment.objects.filter(is_public=True, is_removed=False, content_type=ctype, content_object__in=posts_ids).order_by('-submit_date')[:5]
Comments use GenericForeignKey to store the relation to parent object. Because of the way generic relations work related lookups using __<field> syntax are not supported.
You can accomplish the desired behaviour using the 'in' lookup, however it'll require lot of comparisons when there'll be a lot of BlogPosts.
ids = BlogPost.objects.filter(published=True).values_list('id', flat=True) # Get list of ids, you would probably want to limit number of items returned here
content_type = ContentType.objects.get_for_model(BlogPost) # Becasue we filter only comments for BlogPost
latest_comments = Comment.objects.filter(content_type=content_type, object_pk__in=ids, is_public=True, is_removed=False, ).order_by('submit_date').reverse()[:5]
See the Comment model doc for the description of all fields.
You just cannot do that in one query. Comments use GenericForeignKey. Documentation says:
Due to the way GenericForeignKey is implemented, you cannot use such
fields directly with filters (filter() and exclude(), for example) via
the database API.