Nested resources in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested resource URL handling

Consider a REST API where /users/{userId}/posts/{postId} returns a specific post of a user. What is the output of the following request handler when called with /users/5/posts/10?

Rest API

def get_post(user_id, post_id):
    return f"User {user_id} requested post {post_id}"

A "User 5 requested post 10"

B "User 10 requested post 5"

C "Post 10 of user 5 not found"

D "Error: Invalid user or post ID"

💡 Hint

Look carefully at the order of parameters in the function and the URL.

The URL /users/5/posts/10 maps user_id=5 and post_id=10. The function returns a string with these values in order.

🧠 Conceptual

intermediate

Understanding nested resource URL structure

Which of the following URLs correctly represents a nested resource where comments belong to a specific post?

A /comments/123/posts/456

B /posts/comments/123/456

C /posts/456/comments/123

D /posts/123/456/comments

💡 Hint

Think about the hierarchy: comments belong to posts, so posts come first in the URL.

Nested resources are structured from parent to child. So /posts/456/comments/123 means comment 123 of post 456.

🔧 Debug

advanced

Identify the error in nested resource route definition

Given the following Flask route definitions, which option correctly identifies the error?

@app.route('/users//posts/')
def get_post(user_id, post_id):
    return f"User {user_id} post {post_id}"

@app.route('/users//posts')
def get_posts(user_id):
    return f"Posts for user {user_id}"

@app.route('/posts/')
def get_post_global(post_id):
    return f"Post {post_id} globally"

A There is no error; all routes are correctly defined.

B The function get_post is missing a return statement.

C The route '/users/<int:user_id>/posts' should be defined after '/users/<int:user_id>/posts/<int:post_id>'.

D The route '/posts/<int:post_id>' conflicts with '/users/<int:user_id>/posts/<int:post_id>' causing ambiguity.

💡 Hint

Consider how Flask matches routes and if any overlap can cause confusion.

There is no error; all routes are correctly defined. Flask matches routes in the order defined, with more specific routes first. The global '/posts/' does not conflict with nested user routes as paths differ.

📝 Syntax

advanced

Correct syntax for nested resource route in Express.js

Which of the following Express.js route definitions correctly handles a nested resource for /users/:userId/posts/:postId?

A app.get('/users/:userId/posts/:postId', (res, req) => { res.send(`User ${req.params.userId} Post ${req.params.postId}`); });

B app.get('/users/:userId/posts/:postId', (req, res) => { res.send(`User ${req.params.userId} Post ${req.params.postId}`); });

C app.get('/users/:userId/posts/:postId', (req, res) => { res.send('User ' + req.userId + ' Post ' + req.postId); });

D app.get('/users/:userId/posts/:postId', (req, res) => { res.send(`User ${req.params.postId} Post ${req.params.userId}`); });

💡 Hint

Remember the order of parameters in Express route handlers and how to access URL parameters.

Option B correctly uses req and res in order and accesses req.params for URL parameters.

🚀 Application

expert

Number of items returned by nested resource query

In a REST API, the endpoint /users/7/orders returns all orders for user 7. The database has the following data:

• User 7 has 3 orders: IDs 101, 102, 103
• User 8 has 2 orders: IDs 201, 202

If the API code filters orders by user ID correctly, how many items will the response contain when calling /users/7/orders?

A 5

B 2

C 0

D 3

💡 Hint

Count only orders belonging to user 7.

The endpoint returns orders only for user 7, who has 3 orders.