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POIs it possible to connect different Product-objects to one Contract?
 

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  1. POIs it possible to connect different Product-objects to one Contract?
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    <p><strong>My problem</strong>:<br> I want my Customers to be able to connect many different Products to one Contract, and the code to list all Products attached to a Contract feels dirty. </p> <p><strong>My Models</strong> </p> <pre><code>class Contract(models.Model): # The contract, a customer can have many contracts customer = models.ForeignKey(Customer) class Product(models.Model): # A contract can have many different products contract = models.ForeignKey(Contract) start_fee = models.PositiveIntegerField() # A customer may have ordered a Car, a Book and a HouseCleaning, # 3 completly different Products class Car(Product): brand = models.CharField(max_length=32) class Book(Product): author = models.ForeignKey(Author) class HouseCleaning(Product): address = models.TextField() </code></pre> <p>To list all the products connected to a Contract, the code looks something like this:</p> <pre><code>c = Contract.objects.get(pk=1) for product in c.product_set.all(): print product.book # Will raise an Exception if this product isnt a Book </code></pre> <p>I can't find any sane way to find out what kind of product a Product is!</p> <p><strong>My current solution</strong><br> I've solved it like this... but this whole mess feels... wrong. I'd be happy for any pointers in the right direction.</p> <pre><code>class Product(models.Model): # (as above + this method) def getit(self): current_module = sys.modules[__name__] classes = [ obj for name, obj in inspect.getmembers(current_module) if inspect.isclass(obj) and Product in obj.__bases__ ] for prodclass in classes: classname = prodclass.__name__.lower() if hasattr(self, classname): return getattr(self, classname) raise Exception("No subproduct attached to Product") </code></pre> <p>So i can fetch each specific product like this (pseudo-ish code) :</p> <pre><code>c = Contract.objects.get(pk=1) for product in c.product_set.all(): print product.getit() </code></pre> <p>to list all the "real" products, and not just the baseproduct instance.</p> <p><strong>What I need help with</strong><br> Sugggestions to do this in some kind of sane way.<br> I don't mind having to abstract everything away a bunch of steps, just to get cleaner code.</p>
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