02-books-site.md

Homework 2: 📚 Books Site

Purpose (Why should I do this?)

This assignment is designed for you to practice creating models and relating them using one-to-many and many-to-many relationships.

Scoring is as follows:

Criteria	Possible
Create Book Model	10
Create Author Model	10
Relate Book & Author Models	10
Create Tag Model	10
Filter Books	10
Create Book List View	10
Create Book Detail View	10
TOTAL	70

Instructions - Part 1: Creating your Models

Start a Django project called books_site. In it, create an app books. Make sure you add books to your project's INSTALLED_APPS.

Create Book Model (10 Points)

In books/models.py, create a model called Book and give it the following fields:

• title: Should be a CharField
• num_pages: Should be an IntegerField
• date_published: Should be a DateField

Make sure you add a method __str__ to your model that returns the book's title.

Run python3 manage.py makemigrations and python3 manage.py migrate to migrate your shiny new model.

In the Django shell, create a new Book instance for your favorite novel:

>>> from books.models import *
>>> book1 = Book(title='Harry Potter', num_pages=300, date_published='1997-06-26')
>>> book1.save()

Create at least 2 more books in the same way as above.

Then, do a database query to check that your books were created:

>>> all_books = Book.objects.all()
>>> all_books

Pretty cool!

Create Author Model (10 Points)

Create another model called Author that has the following fields:

• name: Should be a CharField
• birth_date: Should be a DateField

Make sure you add a method __str__ to your model that returns the author's name.

Migrate your models again, and create a few Author objects in your database. Here is an example of one:

>>> author1 = Author(name='J.K. Rowling', birth_date='1965-07-31')
>>> author1.save()

Relate Book & Author Models (10 Points)

Now, add another field to your Book model for the author. This should be a ForeignKey field and should reference the Author model class.

In the field definition, specify null=True so that our previous Book instances (which don't have authors) are still valid.

Migrate your models, and make sure you don't get any errors. Then, modify the previous Book model instances to include their author.

Here is an example of how to do that:

# Retrieve the object from the database
>>> book1 = Book.objects.get(title='Harry Potter')

>>> author1 = Author.objects.get(name='J.K. Rowling')

>>> book1.author = author1
>>> book1.save()

Create Tag Model (10 Points)

Create another model called Tag. A tag should only have a single field, name, that specifies the name of the tag. A tag represents some characteristic of a book - e.g. "fiction", "nonfiction", "young adult", "fantasy", etc. A book can have multiple tags, and a tag can apply to multiple books, so this is a many-to-many relationship.

In your Book model, create another field called tags that is a ManyToManyField. You don't need a Through relationship for this one.

Migrate your models again. Create some Tags in the database, then add some tags to one of your Book objects:

>>> tag1 = Tag.objects.create(name='Fantasy')
>>> book1 = Book.objects.get(title='Harry Potter')

>>> book1.tags.add(tag1)
>>> book1.save()

Filter Books (10 Points)

Next, let's try filtering our books.

To filter by a specific author, we can use a filter like this:

>>> book_list = Book.objects.filter(author__name='J.K. Rowling')
>>> book_list

This should print all of the books in your list written by J.K. Rowling. The double-underscore in author__name acts the same as author.name would in normal Python code.

Create a file in your project's root folder called README.md. In it, answer the following questions:

1. How would we filter for all books with titles containing the word 'Django'?
2. How would we filter for all books with tag 'Fiction'?
3. How would we filter for all authors who have written books containing the word 'Django'? HINT: We can use the book field to refer to an author's books, even though the Author model doesn't explicitly contain it!

Instructions - Part 2: Views

Now, let's display this data in our app!

Create Book List View (10 Points)

In books_site/urls.py, create a URL entry to re-route all web requests (hint: use the empty string '') to your book app's URLs file.

Create a books/urls.py file and in it, create a URL entry for the homepage URL '' and connect it to a view called home.

In books/views.py, create a view function home. This home view should display all books in the database in a list. This time, instead of just returning a string, we are going to call render to render from a template.

Read the documentation on the render function and try writing a view function that renders a template called home.html. In the context variable, you should pass a list of all Book objects.

Then, take a look at the solution below:

from django.shortcuts import render
from .models import Book

def home(request):
  context = {
    'books': Book.objects.all()
  }
  return render(request, 'home.html', context)

Next, create a new folder in books called templates. In it, make a file home.html to display your data:

<h1>All Books</h1>

<ul>
  {% for book in books %}
    <li>
      <a href="/book/{{ book.id }}">{{ book.title }}</a>
    </li>
  {% endfor %}
</ul>

Run your server, and check that everything works! When you load localhost:8000 in your browser, you should see the list of books!

What happens when you click on a specific book's title? You should get "Page Not Found"!

Create Book Detail View (10 Points)

Next, let's make a detail page to display each book. In your books/urls.py file, create another URL entry for book/<int:book_id>/ and connect it to a view function called detail.

The detail view function should take in the request object and the book_id parameter. It should construct a context variable that includes the specific book that has that given id, then render a template detail.html.

Try writing this on your own, then take a look at the solution:

def detail(request, book_id):
  context = {
    'book': Book.objects.get(id=book_id)
  }
  return render(request, 'detail.html', context)

Now, create a template in books/templates called detail.html that displays information about the book: its title, number of pages, publish date, author, author's birth date, and tags.

When you are finished, your detail page should look like this:

Submission

Submit your finished homework using our class submission site.

Resources

1. Django Models
2. Model Field Reference
3. Making Queries

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