我可以在如何将外键保存到模型中获得帮助吗？

Question

I have two models Order and OrderItem .

The process to make an order starts with the OrderItem model.

 class OrderItem(SmartModel):
        shopping_id = models.CharField(max_length=50,db_index=True)
        quantity = models.IntegerField(default=0)
        item = models.ForeignKey(Item)
        order = models.ForeignKey(Order,null=True,blank=True)

OrderItem represents an item and is a modelform with one field being quantity others are excluded i validate the form and create the item like so,

def show_item(request,id):
    # need to evaluate the HTTP method
    if request.method == 'POST':
        a = Item.objects.get(pk=id)
        form = PartialOrderItemForm(request.POST,instance=a)
        # check validation of posted data
        if form.is_valid():
            order.add_to_order(request,a)
            # if test cookie worked, get rid of it
            if request.session.test_cookie_worked():
                request.session.delete_test_cookie()
            url =urlresolvers.reverse('order_index')
            # redirect to order page
            return HttpResponseRedirect(url)
    else:
        form = PartialOrderItemForm()
    request.session.set_test_cookie()
    context={

        'form':form,

    }
    return render_to_response('item.html',context,context_instance=RequestContext(request))

the function called after is_valid ie order.add_to_order creates and saves an item.

def add_to_order(request,obj):  
    postdata = request.POST.copy()
    #get quantity added, return 0 if empty
    quantity = postdata.get('quantity',0)
    # fetch the item or return  missing page error_message
    i = get_object_or_404(Item,pk=obj.id)
    # get items in order
    order_items = get_order_items(request)
    item_in_orders = False
    # check to see if item is already in order
    for order_item in order_items:
        if order_item.item.id == i.id:
            #update the quantity if found
            order_item.augment_quantity(quantity)
            item_in_orders = True
    if not item_in_orders:
        # creat and save a new order item
        anon_user = User.objects.get(id=settings.ANONYMOUS_USER_ID)
    oi=OrderItem.objects.create(shopping_id=_shopping_id(request),
                                          quantity=quantity,
                                          item=i,
                                          created_by=anon_user,
                                          modified_by=anon_user)
    oi.save()

when a customer is done creating an item(in the database), they fill in a form which is Order

class Order(SmartModel):
    #each individual status
    SUBMITTED = 1 # the credit card was valid or mobilemoney was recieved.It is ready for us to process the order
    PROCESSED = 2 # After submitted orders are reviewed, we can mark them as processed, letting deliverers know order is ready to be shipped
    DELIVERED = 3 # the order has been processed and approved by the adminstrator(in this case us), it is delivered.
    PICKED_UP =4 # the order has been processed and is picked up by customer
    CANCELLED = 5 # Customer called the company and decided they didnt want to go through with the order either by phone or email.

    # SET OF POSSIBLE STATUSES
    ORDER_STATUSES = ((SUBMITTED,'Submitted'),(PROCESSED,'Processed'),(DELIVERED,'Delivered'),(PICKED_UP,'picked_up'),(CANCELLED,'Cancelled'),)
    #Order info
    date = models.DateTimeField(auto_now_add=True)
    status = models.IntegerField(choices=ORDER_STATUSES, default=SUBMITTED)
#   customer = models.ForeignKey(Customer,null=True,blank=True,help_text="The customer who made this order",default=None,)
    restaurant = models.ForeignKey(Restaurant,null=True,blank=True,default = None,help_text="The restaurant the customer order from")
    #contact info
    email = models.EmailField(max_length=50,help_text="Needed as alternative")
    mobile = PhoneNumberField(max_length=20,default='+25078######',help_text="Needed to communicate and confirm payment from mobile money")

    #billing information
    billing_name= models.CharField(max_length=50,help_text="Needed so we can deliver to the right individual")

    billing_address= models.CharField(max_length=50,help_text="Needed for delivery purposes, should be office address.")    
    billing_city = models.CharField(max_length=50,help_text="F4L services are only in selected cities.")

Order is a modelform that i validate and save like so.

def show_checkout(request):
    if order.is_empty(request):
        cart_url = urlresolvers.reverse('order_index')
        return HttpResponseRedirect(cart_url)
    if request.method == 'POST':
        postdata = request.POST.copy()
        form = forms.CheckoutForm(request.POST,postdata)
        if form.is_valid():
            anon_user = User.objects.get(id=settings.ANONYMOUS_USER_ID)
            obj = form.save(commit=False)
            obj.created_by = anon_user
            obj.modified_by = anon_user
            obj.save()
            if postdata['submit'] == 'place order':
                reciept_url = urlresolvers.reverse('checkout_reciept')
                return HttpResponseRedirect(reciept_url)
    else:
        form = forms.CheckoutForm
    context = {
        'form':form,
    }
    return render_to_response('checkout/checkout.html',context,context_instance=RequestContext(request))

i should point out that OrderItem is called before Order ..much of where the confusion is coming from to return all OrderItem objects related to Order i do as suggested by the django documentation https://docs.djangoproject.com/en/dev/topics/db/queries/#following-relationships-backward

>>> from orders.models import OrderItem,Order
>>> a = Order.objects.get(id=1)
>>> a
<Order: blah blah blahbaah@blahblah.com +250780000000 1 2013-02-26 17:25:23.138738+00:00>
>>> a.orderitem_set.all()
[]

I am thinking its empty because i didnt save the foreignkey, but i am really confused about how to go about that. Any help is appreciated..

Answer 1

You just need to pass in (or somehow obtain) the object for the order.

Assuming the PK of the order is in your POST vars, you could do this:

def add_to_order(request,obj):  
    postdata = request.POST.copy()
    order = Order.objects.get(pk=postdata.get('order_id'))
    …
        oi=OrderItem.objects.create(order=order, shopping_id=_shopping_id(request), …)

Based on your comment below though, you're creating your order AFTER you create the orderitem , making the code above pointless.

If the order hasn't been created yet, there's absolutely no way for you to tie the order item to the order. At least not without doing something else.

Here's what I'd do.

1. Add a new field to your OrderItem:

    order_uuid = models.CharField(max_length=25, blank=False, null=True) 

2. When you start your order process (wherever you start it), create a UUID using python's uuid package:

    import uuid temporary_order_uuid = uuid.uuid4() 

3. Pass this value through each of your order steps, final saving it to the orderitem when you create it.

    oi=OrderItem.objects.create(order_uuid=temporary_order_uuid, …) 

4. After you create your order , go back and update all orderitems that contain that uuid with the order's pk:

    order_items = OrderItems.objects.get(order_uuid=temporary_order_uuid) for oi in order_items: oi.order = order oi.save() 

5. A much cleaner solution would be to create your orderitems AFTER you create the order in the database, but I don't know all the various requirements of your app.