You should be able to list all of a samurai's items by doing the
following:
samurai = Samurai.objects.get(pk=1)
for inv in samurai.inventory_set.all():
print inv.item.name
samurai.inventory_set returns a QuerySet the same way that
Inventory.objects returns a QuerySet, but it only returns inventory
items belonging to that specific samurai.
So this:
s = Samurai.objects.get(pk=1)
s.inventory_set.all()
Is essentially the same as doing this:
s = Samurai.objects.get(pk=1)
Inventory.objects.filter(samurai=s)
I've actually also researched RPG-like environments in Django. Check
out these links, if you haven't already, for some sample code. Seems
to be the best I've found so far.
http://code.google.com/p/django-mmo/
http://www.rkblog.rk.edu.pl/w/p/code-snapshot-ice-isle-django-web-crpg-game/
http://github.com/batiste/django-rpg
sounds like it could be a great project. have fun!
On Feb 19, 2:18 pm, Timothy Kinney <timothyjkin...@gmail.com> wrote:
> Hi Tim,
>
> Thanks for the concrete examples. I actually had exactly what you had coded
> last night, but I got rid of it because having multiple inventories for a
> single samurai seemed counter-intuitive to me. But it sounds like it's the
> best way to get the granularity I want.
>
> Going back to that system I have a different problem then. If I want to list
> all of the items that a samurai has in his inventory I would like to use a
> samurai.item_set method, but this method fails with multiple inventories. It
> also didn't seem to work with a samurai.inventory_set method.
>
> I'm okay with having multiple inventories for one samurai, but what is the
> best practice for accessing them all as one inventory?
>
> I apologize for the intensive questioning. I hope this discussion is helping
> other users who are new to django. I had searched extensively for django
> implementations of RPG-like inventories and characters and didn't find any.
> I'm sure there are other people in the same boat.
>
> Cheers.
>
> -Tim
>
> On Fri, Feb 19, 2010 at 7:49 AM, Tim Shaffer <timster...@gmail.com> wrote:
> > Basically what you are trying to do is called a many-to-many
> > relationship with an intermediary table.
>
> > If it was a regular many-to-many relationship, you could just do
> > ManyToManyField(Item) on the samurai model, and there would be a table
> > with a foreign key to item, and a foreign key to samurai, and nothing
> > else. But since you need to specify attributes about each of those
> > relationships (in this case, condition), you have to use an
> > intermediary table (Inventory) with those foreign keys, plus your
> > additional attributes. It's not uncommon thing to do at all.
>
> > So if you are using an Inventory class like that, you would want to
> > have this:
>
> > item = models.ForeignKey(Item)
>
> > instead of this:
>
> > item_id = models.ManyToManyField(Item)
>
> > Think of one inventory record as one item belonging to one samurai,
> > with a condition. So if a samurai has more than one of the same same
> > item, he would have more than one inventory record.
>
> > If you were creating your models starting from scratch, you might come
> > up with Inventory usage that looks something like this (pseudo code):
>
> > Inventory.create(samurai='Tim', item='Item 1', condition='100%')
> > Inventory.create(samurai='Tim', item='Item 1', condition='75%')
> > Inventory.create(samurai='Tim', item='Item 2', condition='100%')
>
> > Looking at this, you can determine that each inventory has only one
> > item (foreign key to item), one samurai (foreign key to samurai), and
> > one condition (just an integer). So then you can take that and
> > translate it to a Django model:
>
> > class Inventory(models.Model):
> > samurai = models.ForeignKey('Samurai')
> > item = models.ForeignKey(Item)
> > condition = models.IntegerField(default=100, blank=True,
> > verbose_name='condition')
>
> > Hope this helps.
>
> > On Feb 19, 3:53 am, Timothy Kinney <timothyjkin...@gmail.com> wrote:
> > > Okay, I'm still lacking understanding on the inventory part. Here's what
> > I
> > > have so far:
>
> > > class Inventory(models.Model):
> > > id = models.AutoField(primary_key=True, verbose_name="inventory")
> > > samurai_id = models.ForeignKey('Samurai')
> > > item_id = models.ManyToManyField(Item)
> > > condition = models.IntegerField(default=100, blank=True,
> > > verbose_name='condition')
>
> > > This has almost all the functionality I want. I can assign a single
> > > inventory to a single samurai, and I can add multiple items to the
> > > inventory. The problem is that I can't associate a unique condition (100%
> > or
> > > less) with each item. And I can't seem to add the same item twice.
>
> > > I would like to have an inventory that looked like this:
>
> > > Inventory for Samurai Sam:
> > > (item - condition)
> > > Item1 - 100%
> > > Item1 - 75%
> > > Item2 - 100%
>
> > > -Tim
>
> > > On Thu, Feb 18, 2010 at 7:27 PM, Tim Shaffer <timster...@gmail.com>
> > wrote:
> > > > 1) You can change this in your model. Check out "verbose_name" and
> > > > "verbose_name_plural" for the model's Meta class.
>
> > > >http://docs.djangoproject.com/en/dev/ref/models/options/
>
> > > > 2) If you have a ManyToMany field to samurai on the item, you don't
> > > > need the inventory model at all. A samurai's inventory could be
> > > > obtained by doing "samurai.item_set" and it would return all their
> > > > items. There are different reasons to do each one. However.....
>
> > > > 3) Duplicates can be done by using the Inventory model. You could
> > > > either add a new field called quantity, or simply have multiple
> > > > Inventory records per item and samurai. If each item can have specific
> > > > attributes (for example, I can have 2 of the same item, one of which
> > > > has 55% durability, and the other has 70% durability) you would want
> > > > to have separate records, and could put these attributes on the
> > > > inventory model or item model. But if each item is the same, it's
> > > > easier to just use a quantity field.
>
> > > > 4) If status is a field that could have changing options, create a
> > > > Status model and do a ForiegnKey(Status) on the item. If the choices
> > > > aren't going to change frequently, the choices field could be an
> > > > Integer or String field and use the Django choices functionality.
>
> > > >http://www.djangoproject.com/documentation/models/choices/
>
> > > > I gather that you may not have a ton of experience working with
> > > > relational databases. Perhaps an article on basic database design
> > > > might help. It's best to really understand how a relational database
> > > > works and should be designed before trying to work with Django's ORM.
>
> > > >http://www.deeptraining.com/litwin/dbdesign/FundamentalsOfRelationalD.
> > ..
>
> > > > On Feb 18, 3:17 pm, Timothy Kinney <timothyjkin...@gmail.com> wrote:
> > > > > Hello, I'm new to Django, but learning as fast as I can. I would
> > > > > appreciate some technical help and some database design advice...
>
> > > > > **
> > > > > 1) Admin pluralizing question
>
> > > > > So I have three models: samurai, item, inventory
>
> > > > > When I login to the admin screen it has chosen to pluralize them as:
> > > > > samurais, items, inventorys
>
> > > > > I'm a little bit anal, so this bothers me. Where can I change it to:
> > > > > samurai, items, inventories ?
>
> > > > > **
> > > > > 2) Model relationships question
>
> > > > > Can someone validate that I am using the right relations for these?
> > > > > Users will login with a unique id and instantiate a samurai, each
> > > > > possessing various attributes (not shown below). Items have unique
> > IDs
> > > > > but many samurai can have many of the same items (including
> > > > > duplicates)- also the items have a status as to the condition of the
> > > > > item. There is one inventory for each samurai which links his items
> > to
> > > > > him. Based on this system, I believe I should do the following...
>
> > > > > Samurai model: AutoField ID (primary key, unique)
> > > > > Item model: AutoField ID (primary key, unique), ManyToMany(Samurai)
> > > > > Inventory: Foreignkey(Samurai), ManyToMany(Item)
>
> > > > > Did I do this right?
>
> > > > > **
>
> > > > > And two design questions:
>
> > > > > 3) How should I implement duplicates of items for a single inventory?
> > > > > For example, one samurai may have two identical fish. Should I store
> > > > > this as an additional field in the inventory? If so, how do I link it
> > > > > to the item id? Is it cleaner/faster/better to use a dictionary?
> > > > > Actually, I've never heard of a dict in SQL.
>
> > > > > 4) How should I implement the status/condition of the items? For
> > > > > example, I want them to be "New", "Used", or "Broken/Unusable".
> > Should
> > > > > I store this in the inventory or in a separate model called Status?
> > If
> > > > > the latter, should I use a foreignkey(item) and OneToOne(Inventory)
> > or
> > > > > something else?
>
> > > > > Thank you very much for your help. If you are aware of any tutorials
> > > > > or available source code for coding RPGs, browser games, or
> > > > > inventories, I will be happy to follow links and try to learn on my
> > > > > own.
>
> > > > > -Tim
>
> > > > --
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