Related name for reverse access in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a ForeignKey with a related name for reverse access.

Django

class Book(models.Model):
    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name=[1])

Drag options to blanks, or click blank then click option'

A"author"

B"books"

C"book_author"

D"authors"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the model name 'author' as related_name causes confusion.

Omitting quotes around the related_name string.

The related_name defines the name to access all books from an author instance, so "books" is a clear and common choice.

2fill in blank

medium

Complete the code to access all books of an author using the related name.

Django

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

Drag options to blanks, or click blank then click option'

Abooks

Bbook_set

Cauthor_books

Dbook

Attempts:

3 left

💡 Hint

Common Mistakes

Using the default book_set when a related_name is set.

Using singular form which is incorrect for reverse access.

You use the related_name defined in the ForeignKey to access related objects. Here, books is the correct related name.

3fill in blank

hard

Fix the error in the ForeignKey definition to correctly set the related name.

Django

class Comment(models.Model):
    post = models.ForeignKey(Post, on_delete=models.CASCADE, related_name=[1])

Drag options to blanks, or click blank then click option'

A"comments"

B"comment"

C"post_comments"

D"post"

Attempts:

3 left

💡 Hint

Common Mistakes

Using singular related_name causing confusion in reverse queries.

Using the model name 'post' which conflicts with the ForeignKey field name.

The related_name should be plural to represent multiple comments related to a post, so "comments" is correct.

4fill in blank

hard

Fill both blanks to define a ForeignKey with a related name and access the related objects.

Django

class Entry(models.Model):
    blog = models.ForeignKey(Blog, on_delete=models.CASCADE, related_name=[1])

entries = blog.[2].all()

Drag options to blanks, or click blank then click option'

A"entries"

B"entry_set"

Centries

D"blogs"

Attempts:

3 left

💡 Hint

Common Mistakes

Using default entry_set when related_name is set.

Mismatch between related_name and access attribute.

The related_name is set to "entries", so accessing related objects uses the same name.

5fill in blank

hard

Fill all three blanks to define a ForeignKey with a related name, access related objects, and filter them.

Django

class Review(models.Model):
    product = models.ForeignKey(Product, on_delete=models.CASCADE, related_name=[1])

reviews = product.[2].filter(rating__[3]=5)

Drag options to blanks, or click blank then click option'

A"reviews"

Breviews

Cgte

Dlte

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong related_name causing attribute errors.

Using incorrect filter lookup like 'lte' instead of 'gte'.

The related_name is "reviews", so you access product.reviews. The filter uses rating__gte=5 to get reviews with rating 5 or higher.

Practice

1. What does the related_name attribute do in a Django model's ForeignKey field?

easy

A. It sets the name used to access related objects from the other model.

B. It changes the database table name for the model.

C. It defines the primary key of the model.

D. It specifies the default ordering of query results.

Solution

1. Step 1: Understand the purpose of related_name

   The related_name attribute defines how you access related objects from the reverse side of a ForeignKey relationship.

2. Step 2: Identify what related_name affects

   It does not affect table names, primary keys, or ordering but sets the attribute name for reverse access.

3. Final Answer:

   It sets the name used to access related objects from the other model. -> Option A

4. Quick Check:

   related_name = reverse access name [OK]

Hint: related_name names reverse access from related model [OK]

Common Mistakes:

• Confusing related_name with table name
• Thinking it sets primary key
• Assuming it controls query ordering

2. Which of the following is the correct way to set a related_name in a Django ForeignKey field?

easy

A. author = models.ForeignKey(Author, reverse_name='books', on_delete=models.CASCADE)

B. author = models.ForeignKey(Author, related='books', on_delete=models.CASCADE)

C. author = models.ForeignKey(Author, related_name='books', on_delete=models.CASCADE)

D. author = models.ForeignKey(Author, relation_name='books', on_delete=models.CASCADE)

Solution

1. Step 1: Recall correct attribute name

   The correct attribute to set reverse access name is related_name.

2. Step 2: Check syntax correctness

   author = models.ForeignKey(Author, related_name='books', on_delete=models.CASCADE) uses related_name='books' correctly; others use incorrect attribute names.

3. Final Answer:

   author = models.ForeignKey(Author, related_name='books', on_delete=models.CASCADE) -> Option C

4. Quick Check:

   Use related_name= for reverse access [OK]

Hint: Use exact attribute name 'related_name' in ForeignKey [OK]

Common Mistakes:

• Using 'related' instead of 'related_name'
• Using 'reverse_name' or 'relation_name' which don't exist
• Missing on_delete argument

3. Given these models:

class Author(models.Model):
    name = models.CharField(max_length=100)

class Book(models.Model):
    author = models.ForeignKey(Author, related_name='books', on_delete=models.CASCADE)
    title = models.CharField(max_length=100)

What will author.books.all() return?

medium

A. All Author objects related to that Book instance.

B. All Book objects related to that Author instance.

C. A syntax error because 'books' is not defined.

D. An empty queryset always.

Solution

1. Step 1: Understand related_name usage

   The related_name='books' allows accessing all Book objects from an Author instance using author.books.

2. Step 2: Interpret the method call

   author.books.all() returns a queryset of all Book objects linked to that Author.

3. Final Answer:

   All Book objects related to that Author instance. -> Option B

4. Quick Check:

   author.books.all() = related books [OK]

Hint: related_name lets you get all related objects easily [OK]

Common Mistakes:

• Thinking it returns Author objects
• Assuming syntax error due to related_name
• Expecting empty queryset without data

4. Identify the error in this model definition:

class Comment(models.Model):
    post = models.ForeignKey(Post, related_name='post', on_delete=models.CASCADE)
    text = models.TextField()

What problem will this cause?

medium

A. It will cause a syntax error because related_name cannot be 'post'.

B. It will cause a runtime error because TextField is not allowed here.

C. It will work fine without any issues.

D. It will cause a reverse accessor clash if Post already has a field named 'post'.

Solution

1. Step 1: Understand related_name uniqueness

   The related_name must be unique per model to avoid clashes.

2. Step 2: Analyze the name 'post'

   If Post model already has a field or reverse accessor named 'post', this causes a clash error.

3. Final Answer:

   It will cause a reverse accessor clash if Post already has a field named 'post'. -> Option D

4. Quick Check:

   related_name must be unique to avoid clashes [OK]

Hint: Avoid related_name same as model or field names [OK]

Common Mistakes:

• Assuming related_name can be any string without conflict
• Thinking related_name causes syntax error
• Believing TextField is invalid here

5. You have these models:

class Category(models.Model):
    name = models.CharField(max_length=50)

class Product(models.Model):
    category = models.ForeignKey(Category, on_delete=models.CASCADE)

You want to access all products of a category using category.items.all(). How should you modify the ForeignKey?

hard

A. Add related_name='items' to the ForeignKey in Product.

B. Change ForeignKey to ManyToManyField with related_name='items'.

C. Rename the ForeignKey field to 'items'.

D. Add related_query_name='items' to the ForeignKey.

Solution

1. Step 1: Understand reverse access naming

   To use category.items.all(), the ForeignKey must have related_name='items'.

2. Step 2: Check other options

   Changing to ManyToManyField or renaming the field won't create the desired reverse attribute. related_query_name affects query filters, not attribute names.

3. Final Answer:

   Add related_name='items' to the ForeignKey in Product. -> Option A

4. Quick Check:

   related_name sets reverse attribute name [OK]

Hint: Set related_name='items' to get category.items [OK]

Common Mistakes:

• Confusing related_name with related_query_name
• Changing field name instead of related_name
• Switching to ManyToManyField unnecessarily