How to data fetch by using has many through in django?

Question

I am learning django. I have a simple model named customer. Here is my model:

class Year(models.Model):
    year = models.CharField(max_length=255)
    created_at = models.DateTimeField(auto_now=False, auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True, auto_now_add=False)

    def __unicode__(self):
        return self.year

    def __str__(self):
        return self.year


class Customer(models.Model):
    name = models.CharField(max_length=255)
    created_at = models.DateTimeField(auto_now=False, auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True, auto_now_add=False)

    def __unicode__(self):
        return self.name

    def __str__(self):
        return self.name


class Product(models.Model):
    customer_name = models.ForeignKey(Customer, on_delete=models.CASCADE)
    quantity = models.CharField(max_length=255)
    year = models.ForeignKey(Year, on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now=False, auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True, auto_now_add=False)

    def __unicode__(self):
        return self.score

    def __str__(self):
        return self.score

here is my view of customer:

from django.shortcuts import render, get_object_or_404, redirect
from .models import Customer, Product, Year


# Create your views here.
def home(request):
    customer = Customer.objects.all
    product = Product.objects.all

    year = Year.objects.all().prefetch_related('product_set')

    context = {'customers': customer,
               'years': year,
               'products': product
               }
    return render(request, 'customer.html', context)

Here is my customer.html

{% extends 'base.html' %}
{% block customer %}
<div class="container">
  <h2>Players Table</h2>
  <p>Customer with Product</p>
  <table class="table">
    <thead>
      <tr>
          <th>Year/Product</th>
          {% for customer in cutomers %}
              <th>{{ customer.name }}</th>
          {% endfor %}
      </tr>
    </thead>
      <tbody>


{#      <tr>#}
{#          <th>2011</th>#}
{#          <th>633</th>#}
{#          <th>424</th>#}
{#      </tr>#}
{#      <tr>#}
{#          <th>2012</th>#}
{#          <th>353</th>#}
{#          <th>746</th>#}
{#      </tr>#}
      </tbody>
  </table>
</div>

{% endblock customer %}

Now I have to generate table row which will contain year,customer and product througth customer per year. So that How to fetch for every row that contains year, year based customer product data.

More simple, Year has many customers and customer has one product thought year.

How to generate this. Please help me.

Answer 1

You don't need product or year in your context. You can use relation between your models to get this information:

views.py

from django.shortcuts import render, get_object_or_404, redirect
from .models import Customer, Product, Year

# Create your views here.
def home(request):
    customer = Customer.objects.all
    context = {'customers': customer}
    return render(request, 'customer.html', context)

Now in your template you can get :

All product of a customer, with year by product

{% for customer in customers %}
   Customer : {{ customer }}<br>
   {% for product in customer.product_set.all %}
       Product : {{ product }} / Year :{{ product.year }}<br>
   {% endfor %}
{% endfor %}

But I don't like put too much logic in template. I advise you to create the data of your table in your view, even better in your model. And then generate your html table with this data.

Summary of the function you will need: You can replace all() by a filter()

products = customer.product_set.all() # give you all product of a customer

UPDATE AFTER COMMENTS:

Views.py

from django.shortcuts import render, get_object_or_404, redirect
from .models import Customer, Product, Year

# Create your views here.
def home(request):
    customers = Customer.objects.all()
    years = Year.objects.all().values_list('year', flat=True).asc() # List of year name 
    rows = []
    for year in years:
        row = [year] + [None] * len(customers) # Row with year in first column, and the rest init with same size of customers list
        for idx, customer in enumerate(customers):
            quantities = customer.product_set.filter(year__year=year).valu e_list('quantity', flat=True) # filter product by year. That can return multiple product !!! 
            row[idx + 1] = ' ,'.join(quantities) # create a string of quantities
        rows.append(row) # Add new row in our rows list
    context = {'customers': customer,
               'rows': rows}
    return render(request, 'customer.html', context)

template:

{% extends 'base.html' %}
{% block customer %}
<div class="container">
  <h2>Players Table</h2>
  <p>Customer with Product</p>
  <table class="table">
    <thead>
      <tr>
          <th>Year/Product</th>
          {% for customer in customers %}
              <th>{{ customer.name }}</th>
          {% endfor %}
      </tr>
    </thead>
      <tbody>
        {% for row in rows %}
            <tr>
                {% for cell in row %}
                    <th>cell</th>
                {% endfor %}
            </tr>
        {% endfor %}
      </tbody>
  </table>
</div>

I think that can help you to understand how to resolve your problem. I don't test this code, so maybe there is error. This is not perfect !