title: Django Admin list_display product list
body: <p>I new in django and I trying modifying a project to learn.</p>
  
  <p>I've two classes in a model ('Order' and 'OrderItem'), the class OrderItem stores all items selected in a client order.</p>
  
  <blockquote>
    <p>models.py</p>
  </blockquote>
  
  <pre><code>class Order(models.Model):
  
      STATUS_CHOICES = (
          (0, 'Waiting Payment'),
          (1, 'Completed'),
          (2, 'Canceled'),
      )
  
      PAYMENT_OPTION_CHOICES = (
          ('deposit', 'deposit'),
          ('paypal', 'Paypal'),
      )
  
      user = models.ForeignKey(settings.AUTH_USER_MODEL, verbose_name='User')
      status = models.IntegerField(
          'Situation', choices=STATUS_CHOICES, default=0, blank=True
      )
      payment_option = models.CharField(
          'Payment Options', choices=PAYMENT_OPTION_CHOICES, max_length=20,
           default='deposit'
      )
  
      created = models.DateTimeField('Created in', auto_now_add=True)
      modified = models.DateTimeField('Modified in', auto_now=True)
  
      objects = OrderManager()
  
      class Meta:
          verbose_name = 'Order'
          ordering = ('-created',)
  
      def __str__(self):
          return 'Order #{}'.format(self.pk)
  
      def products(self):
          products_ids = self.items.values_list('product')
          return Product.objects.filter(pk__in=products_ids)
  
      def total(self):
          aggregate_queryset = self.items.aggregate(
              total = models.Sum(
                  models.F('price') * models.F('quantity'),
                  output_field = models.DecimalField()
              )
          )
          return aggregate_queryset['total']
  
  
  
  class OrderItem(models.Model):
  
      order = models.ForeignKey(Order, verbose_name='Order',     related_name='items')
      product = models.ForeignKey('event.Product', verbose_name='Product')
      quantity = models.PositiveIntegerField('Quantity', default=1)
      price = models.DecimalField('Price', decimal_places=2, max_digits=8)
  
      class Meta:
          verbose_name = 'Order Item'
  
      def __str__(self):
          return '{}'.format(self.product)
  </code></pre>
  
  <p>In the django admin I can show all Orders and when I click to see more I see all products on this order, but my problem is, I can't list this products of class OrderItem in my list_display, how  can I do that?</p>
  
  <blockquote>
    <p>admin.py</p>
  </blockquote>
  
  <pre><code>class OrderItemInline(admin.StackedInline):
      model = OrderItem
      fields = ['product']
      readonly_fields = ['product',]
      extra = 0
      max_num = 0
  
  
  class OrderAdmin(admin.ModelAdmin):
  
      model = Order
      inlines = [ OrderItemInline, ]
  
      readonly_fieldsets = (
          (None, {
              'fields': ('user','status','order','created')
          }),
      )
      readonly_fields = ['user','status','payment_option']
  
      search_fields = ['user__name', 'user__email']
      list_filter = ['status', ]
  
      list_display = ['pk','user','status','created','product']
      ordering = ('-created',)
  
  
     admin.site.register(Order, OrderAdmin)
  </code></pre>