Field

An attribute within a Model class used to track a characteristic of the data.

Definition: CharField

A string.

name = models.CharField(max_length=255)

Definition: TextField

A long string.

quote = models.TextField()

ForeignKey

One-to-Many.

class BookQuote(models.Model):
    book = models.ForeignKey(Book, on_delete=models.CASCADE, related_name='quotes')

Workflow: Implement One-to-Many

1. Add models.ForeignKey(Book).

2. Add on_delete and related_name.

   class Book(models.Model):
       name = models.CharField(max_length=255)
   
   class BookQuote(models.Model):
       book = models.ForeignKey(Book, on_delete=models.CASCADE, related_name='quotes')
   

3. Access data:

   • from BookQuote:

     quote = BookQuote.objects.get(id=1)
     parent_book = quote.book
     

   • from Book:

     book = Book.objects.get(id=1)
     all_quotes = book.quotes.all()
     

4. Save data:

   new_quote = BookQuote(content="To be or not to be", book=book_instance)
   new_quote.save()
   

ManyToManyField

A field used to create a relationship where multiple records in one table can be associated with multiple records in another table.

Workflow: Many-to-Many

1. Add models.ManyToManyField(Author).

2. Add related_name.

   class Author(models.Model):
       name = models.CharField(max_length=255)
   
   class Book(models.Model):
       title = models.CharField(max_length=255)
       authors = models.ManyToManyField(Author, related_name='books')
   

3. Access data:

   • from Book:

     book = Book.objects.get(id=1)
     book_authors = book.authors.all()
     book.authors.add(author_instance)
     

   • from Author:

     author = Author.objects.get(id=1)
     author_books = author.books.all()
     

4. Save data:

   book.authors.add(author_instance)
   book.authors.set([author1, author2])