how to chain field? - django

Question

This my engine models
from django.db import models
class Colors(models.Model):
color_name = models.CharField(max_length=50)
def __unicode__(self):
return self.color_name
This my Cars models
from django.db import models
class Cars(models.Model):
car_model = models.CharField(max_length=50)
car_colors = models.ManytoManyField(Colors, related_name='Car Colors')
def __unicode__(self):
return self.car_model
O.K. Let's see my CarsData Model.
This my CarsData models
from django.db import models
class CarsData(models.Model):
car_barcode= models.CharField(max_length=50)
available_color = ChainedForeignKey(
Cars,
chained_field="car_model",
chained_model_field="car_colors",
show_all=False,
auto_choose=True
)
def __unicode__(self):
return self.car_barcode
My admin.py looks like that:
from django.contrib import admin
from django import forms
from myapp.models import *
class CarsDataAdminForm(forms.ModelForm):
class Meta:
model = CarsData
def __init__(self, *arg, **kwargs):
super(CarsDataAdminForm, self).__init__(*arg, **kwargs)
self.fields['available_color'].choices = [(csc.id,csc.car_colors) for csc in Cars.objects.all()
class CarsDataAdmin(admin.ModelAdmin):
form = CarsDataAdminForm
admin.site.register(CarsData,CarsDataAdmin)
Is there anyway to show in the ChoiceField 'just' color_name field datas? I see just car_model because i have to set it :
def __unicode__(self):
return self.car_model
How can i chain available_colors field to color_name field? I want to show in available_colors choices just color names like red, blue, black, white...
Can you please give me an example?

Answer 1

I think I don't get your code:
class CarsData(models.Model):
car_barcode = models.CharField(max_length=50)
available_color = ChainedForeignKey(
Cars,
chained_field="car_model", # should be a field in THIS model
chained_model_field="car_colors", # should be the matching field
# in the Cars model
show_all=False,
auto_choose=True
)
And both referenced fields must be ForeignKeys to the same (third) model.
Maybe this works, even without changing the AdminForm (I also changed the model names to singular and remove some repetitions, as the most common use dictates):
class Color(models.Model):
name = models.CharField(max_length=50)
def __unicode__(self):
return self.name
class CarModel(models.Model):
model = models.CharField(max_length=50)
available_colors = models.ManytoManyField(Color, through='AvailableColor')
def __unicode__(self):
return self.model
class AvailableColor(models.Model):
car_model = models.ForeignKey(CarModel)
color = models.ForeignKey(Color)
def __unicode__(self):
return unicode(self.color)
class CarData(models.Model):
car_barcode = models.CharField(max_length=50)
car_model = models.ForeignKey(CarModel)
car_color = ChainedForeignKey(
AvailableColor,
chained_field="car_model", # field in CarData
chained_model_field="car_model", # field in AvailableColor
show_all=False,
auto_choose=True
)
You can't do otherwise because you need two models with a matching FK. Using Cars.car_colors.through (that is a valid model on which to query etc) you don't have a good display. With a (dummy) explicit intermediate model you define unicode and the admin should show the correct data.