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Answer 1

+1 A:

This sort of logic is what managers are for. Even if you decide not to use managers, you should be factoring out common code in some other way that you're familiar with. (Prefer procedural programming? Write a utility function. Familiar with OOP? Create callable class-based views which inherit from a class that contains the filtering logic.) If you find yourself copying and pasting code like this, it's a sign that you're going to run into trouble before too long.

ozan 2009-11-24 11:19:40

so how exactly do I go about solving my problem? I'm not so good at Django...this is my first app BTW

Stephen 2009-11-24 11:32:10

Answer 2

A:

You write a manager. From your example it needs at least one method for vehicle_query, one method for .annotate(count=Count('id')) and maybe some for the repeated order_by()s.

If you need the methods to nest, so that you can do vehicle_query(year).with_counts() as well as with_counts().vehicle_query(year), you need to make your own QuerySet too, that is: inherit from QuerySet, add the methods there, then use that queryset in your manager, and map methods in the manager to the methods in the queryset.

from django.db import models
from django.db.models.query import QuerySet

class VehicleQuerySet(QuerySet):
    def vehicle_query(self, year):
        return self.filter(common_vehicle__year__year__exact=year).exclude(status__status='Incoming')

class VehicleManager(models.Manager):
    def get_query_set(self):
        return VehicleQuerySet(self.model)

    def vehicle_query(self, year):
        return self.get_query_set().vehicle_query(year)

class WhateverModel(models.Model):
    ...
    objects = models.Manager() # keeping the default manager
    smart_objects = VehicleManager() # additional manager

Then in your views:

vehicle_query = Vehicle.smart_objects.vehicle_query(year)

kaleissin 2009-11-24 12:22:48

Is there another way of doing this...perhaps using sessions? Maybe it's just me but I can't begin to understand this bit of code

Stephen 2009-11-24 12:48:44

This is a very common way. follow ozan link to learn about managers.

vikingosegundo 2009-11-25 01:46:27

BTW, will this preserve my values in between queries?

Stephen 2009-11-25 04:40:01

Just wondering...is there a way to pass all the values i.e. year, make, series, colour and body style as one function such as vehicle_query?

Stephen 2009-11-26 07:08:47

47, certainly. Either you'll have to return year_count, make_count etc. from a single method, or you'd need a method for each. Have you done the python tutorial? See that for how to return more than one thing at a time in a function/method.

kaleissin 2009-11-29 20:42:55

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Setting up a filter in django

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