Best Model Architecture?

[Avery Laird]

Hi,

I have a question about best practices / tips for making my models a bit less verbose and confusing. For example, I often find when making models for a certain theme that I repeat myself. Let's say we have a page with multiple elements: a slider, two bodies of text (each with their own header), an accordion with it's own header, some quotes from clients, and maybe a some team members. Usually, most of this content layout is consistent through the site, but with different data (except for a few cases, ie it's unlikely the team model would have differing data for different pages). Is there a way to make a class for each element which the page itself can inherit, much like the RichTextField (even though I know RichTextField is not the perfect example)? And if so, what should that model inherit from? Something like this...

class Slider(Orderable):
     # eg

image = FileField(verbose_name=_("Image"),

                      upload_to=upload_to("theme.Slide.image", "slider"),

                      format="Image", max_length=255, null=True, blank=True)
Class Meta:
   # whatever

...would have to define a homepage, and then be initialized as inline in admin.py. Is there a way to instead have the page inherit the model, or at least not access everything through inline (even though it is a model separate from the page)? Or at least, a more streamlined process that doesn't involved me repeating myself?

Thanks in advance for any insight, I hope I explained myself adequately! 

Cheers,

Avery

[Josh Cartmell]

Hi Avery, you should be able to do this:

class SlideBase(models.Model):
     # eg

image = FileField(verbose_name=_("Image"),

                      upload_to=upload_to("theme.Slide.image", "slider"),

                      format="Image", max_length=255, null=True, blank=True)
Class Meta:

   abstract = True

Then:

class Slider(Orderable, BaseSlider):

    pass

The key here is making BaseSlider abstract have a look at the docs if you want to dive in more, https://docs.djangoproject.com/en/1.7/topics/db/models/#abstract-base-classes

[Avery Laird]

Hi Josh,

Thanks for the reply. I actually already use abstract models in many of my projects -- very useful feature! Maybe I should have explained my thinking a bit better. I was describing something more along the lines of the RichTextPage behaviour. I know the mechanics behind the scences of RichTextPage is actually more complicated than this, but the behavior that we see involves a page (eg, class Page(Page, RichTextPage) ) which inherits RichTextPage. Is it possible to do something like that? For example, I know I also want my page to have a slider, so I do: class Page(Page, Slider). Let's say I also want an accordion: class Page(Page, Slider, Accordion). The level lower than that (BaseSlider, BaseAccordion)  would involve the abstract models you talked about above. Being pretty new to django, I have some large gaps in my knowledge which may have prevented me from seeing some glaring error in this thinking --  is this even possible / practical?

Thanks again, I appreciate your help with this!

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[Josh Cartmell]

Gotcha, I think I'm understanding better what you want to do.

I'm not sure this is possible because presumably the Slide class will need a foreignkey to the parent page class that it shows up on, is that correct?  I.e. wouldn't the models really look something like this:

class SliderPage(Page):
    pass


class Slide(Orderable):

    sliderpage = models.ForeignKey(SliderPage, related_name="slides")

    image = FileField(...)

Then wherever you had an instance of a SliderPage you could do:

sliderpage.slides.all()

I don't know of any way to inherit a ForeignKey relationship (that of course doesn't mean it's impossible).

Something else you may be able to do is use a generic foreignkey in some way, https://docs.djangoproject.com/en/1.7/ref/contrib/contenttypes/#generic-relations, that would allow you to have a slide be related to any other model, but it would also complicate things a lot more.

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