Sven, I recommend that you do *not* read this email. The reason is that I have been confused about this issue before, and I am (below) trying to think it through and eliminate some of that confusion.
Maybe tomorrow I'll have a less twisted reply. Let's see if we can get my head straight on this one. A recipe can have a single "categories" and that "categories" element can contain multiple "category" elements. Do we agree so far? If so, the question is: How do we represent that in a Django model? In what is currently generated, the "Recipe" model has a ForeignKey to a "CategoriesType" model. This means that a record in the "Recipe" table (relation) can point to (refer to, be joined with?) multiple records in the "CategoriesType" table. Which is what we want, right? Or am I twisting the fact so that they fit what I want to see? Look at this snippet from the Django documentation (at https://docs.djangoproject.com/en/1.11/topics/db/models/): from django.db import models class Musician(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) instrument = models.CharField(max_length=100) class Album(models.Model): artist = models.ForeignKey(Musician, on_delete=models.CASCADE) name = models.CharField(max_length=100) release_date = models.DateField() num_stars = models.IntegerField() Does the above mean that an "Album" can have multiple musicians, that is references to multiple records in the "Musician" table? Or, does it mean that a musician can have multiple albums? Here is another snippet from the same Web page: Many-to-one relationships¶ To define a many-to-one relationship, use django.db.models.ForeignKey. You use it just like any other Field type: by including it as a class attribute of your model. ForeignKey requires a positional argument: the class to which the model is related. For example, if a Car model has a Manufacturer – that is, a Manufacturer makes multiple cars but each Car only has one Manufacturer – use the following definitions: from django.db import models class Manufacturer(models.Model): # ... pass class Car(models.Model): manufacturer = models.ForeignKey(Manufacturer, on_delete=models.CASCADE) # ... In our case, we want a "Recipe" to have multiple instances of "CategoriesType". So, the should place the ForeignKey in the "CategoriesType" model. So, perhaps the rule we should follow is: If you have Model-A and Model-B and if you want a Model-A to have multiple instances of Model-B, then put the ForeignKey in Model-B (referring to Model-A). What do you think? It worries me that I seem to recall I've been confused about this before. More on this tomorrow. Dave On Mon, Oct 23, 2017 at 08:33:36AM +0200, Sven Prevrhal wrote: > I have an XSD with > > <xs:element name="recipe"> > <xs:complexType> > <xs:sequence> > > <xs:element name="title" type="xs:string"/> > > <xs:element name="categories"> > <xs:complexType> > <xs:sequence> > <xs:element name="category" type="xs:string" minOccurs="1" > maxOccurs="unbounded"/> > </xs:sequence> > </xs:complexType> > </xs:element> > .... > </xs:sequence> > </xs:complexType> > </xs:element> > > The Django models I get from that are > > > class Recipe(models.Model): > title = models.CharField(max_length=1000, ) > categories = models.ForeignKey( > "CategoriesType", > related_name="recipe_categories_categoriesType", > ) > .... > > and > > class CategoriesType(models.Model): > category = models.CharField(max_length=1000, ) > .... > > This seems wrong to me. I would have thought Category gets a ManyToManyField > > to Recipe. The way it comes out of generateDS it looks like a > CategoriesType has many Recipes. Or perhaps my XSD is wrong? > > Cheers, > Sven > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > generateds-users mailing list > generateds-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/generateds-users -- Dave Kuhlman http://www.davekuhlman.org ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ generateds-users mailing list generateds-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/generateds-users
