title: how to chain field?
body: <p>This my engine models</p>
  
  <pre><code>from django.db import models
  
  class Colors(models.Model):
     color_name = models.CharField(max_length=50)
  
      def __unicode__(self):
          return self.color_name
  </code></pre>
  
  <p>This my Cars models</p>
  
  <pre><code>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
  </code></pre>
  
  <p>O.K. Let's see my CarsData Model.</p>
  
  <p>This my CarsData models</p>
  
  <pre><code>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
  </code></pre>
  
  <p>My admin.py looks like that:</p>
  
  <pre><code>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)
  </code></pre>
  
  <p>Is there anyway to show in the ChoiceField 'just' color_name field datas? I see just car_model because i have to set it :</p>
  
  <pre><code>def __unicode__(self):
      return self.car_model
  </code></pre>
  
  <p>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...</p>
  
  <p>Can you please give me an example?</p>