I am writing a Blog-style django site which needs to render a
collection of Item objects. Item is the root Super class for a whole
bunch of sub-classes -- Photo, Video, Quote, News, etc. I want to be
able to iterate through Item.objects.all() and ask each Item to
render() itself based on which sub-class it is. I'm from a C++
background, and my virtual-method approach isn't working -- it just
calls the Item.render() method instead of the appropriate sub-class
one.
#Simplified example classes:
class Item(models.Model):
group = models.ForeignKey(ItemGroup)
order = models.IntegerField()
when = models.DateTimeField(null=True, blank=True, help_text="When
the item occured; can be auto-extracted from photos")
added = models.DateTimeField(default=datetime.datetime.now,
editable=False)
def render(self):
return "Plain 'ol item"
class News(Item):
html = models.TextField()
def render(self):
return "<div class='news'>" + self.html + "</div>"
class Photo(Item):
original = models.FileField(upload_to='%Y/%m')
def render(self):
return "<img src='%s'>" % (self.original.url)
class Quote(Item):
#...
class Video(Item):
#...
# Now I'd like to be able to iterate through all items in a given
group
# (eg. for i in exampleGroup.item_set.order_by("order") )
# and call the render function for each Item, regardless of whether it
# is a News, Photo, Quote, Video, etc. Like a virtual function in C++.
# But i.render() just calls the Item.render() method; how can I figure
out
# which subclass the item is, and call the appropriate subclass
method?
I know this is a bit ugly having HTML in the models, and I should
probably use "inclusion" template tags. Can anyone please point show
me how this should be done?
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