Question

I am somewhat new to Django and have searched for some simple examples of creating objects with subobjects in views so that in templates I can have nested for loops.

Here is my models.py for this application…

from django.db import models
from django import forms

class Market(models.Model):
    name   = models.CharField('Market name', max_length=150)
    state  = models.CharField('State', max_length=2)

    def __unicode__(self):
        return self.name

class Location(models.Model):
    name   = models.CharField('Location name', max_length=150)
    address1  = models.CharField('Address 1', max_length=200)
    address2  = models.CharField('Address 2', max_length=200,blank=True)
    city   = models.CharField('City', max_length=100)
    state   = models.CharField('State', max_length=2)
    zip_code = models.CharField('ZIP', max_length=10)
    phone  = models.CharField('Phone', max_length=20)
    hours  = models.TextField('Hours of operation', max_length=255)
    quote_text = models.TextField('Customer quote', max_length=500)
    quote_by = models.CharField('Customer name', max_length=30)
    yelp_url = models.URLField('Yelp URL', max_length=300,blank=True)
    image_store = models.ImageField('Storefront image', upload_to='images/locations', max_length=300,blank=True)
    image_staff = models.ImageField('Staff image', upload_to='images/locations', max_length=300,blank=True)
    market  = models.ForeignKey(Market, verbose_name='Regional market', null=True)

    def __unicode__(self):
        return self.name

Markets data may look as follows…

id = 1
state = 'MO'
name = 'St. Louis - Central'

id = 2
state = 'MO'
name = 'St. Louis - West'

id = 3
state = 'IL'
name = 'Chicago - South'

id = 4
state = 'IL'
name = 'Chicago - North'

In my views.py I’d like to create an object with a list/array of grouped Market states (distinct) in descending order, each with a subarray of the individual Market names in that State in order to complete a nested forloop in the template.

The templating language in Django is really cool in how it prevents a ton of logic from residing betwixt the html, which I like. But I am still wrapping my head around both Python syntax and the need to create all objects exactly the way they need to iterate in the template.

Here’s what views.py looks like …

def locations_landing(request):
    marketList = Market.objects.values('state').order_by('-state').distinct()
    return render_to_response('locations.html', locals()) 

How to return an object so that my template can perform the following nested looping…

{% for st in stateList.all %}
    <h4>{{ st.state }}</h4>
    {% for mkt in stateList.marketList.all %}
        <p>* <a href="#">{{ mkt.name }}</a></p>
    {% endfor %}
{% endfor %}

This would result in the following rendered in html based on my data samples above…

<h4>MO</h4>
<p>* St. Louis - Central</p>
<p>* St. Louis - West</p>
<h4>IL</h4>
<p>* Chicago - South</p>
<p>* Chicago - North</p>

BTW, there are no errors in any of the .PY code samples above, all is well, I just need some guidance on creating the object correctly in the view so the template does it’s thing.

Answer 1

I don’t see a need to use distinct here. By representing the states as separate model and using relations you would gain much more flexibility.

I suggest you create a third State model and use a ForeignKey to relate the models together so that each Market has a one to many relation to single State, i guess you also want Location model related to the Market model.

class State(models.Model):
    name   = models.CharField('State name', max_length=150)

class Market(models.Model):
    name   = models.CharField('Market name', max_length=150)
    state  = models.ForeignKeyField(State)

class Location(models.Model):
    state  = models.ForeignKeyField(Market)
    ...

In your view, all you need to do is take all the states and pass them into the template:

def locations_landing(request):
    state_list = State.objects.all()
    return render_to_response('locations.html', {'state_list':state_list}) 

And finally, in your template, iterate over the state list and use a backward relation queryset to get all the markets in that state:

{% for state in state_list %}
    <h4>{{ state }}</h4>
    {% for market in state.market_set.all %}
        <p>* <a href="#">{{ market }}</a></p>
        {% for location in market.location_set.all %}
           <p> {{ location }} </p>
        {% endfor %}
    {% endfor %}
{% endfor %}