GraphQL Playground and tools - Mini Project: Build & Apply

Explore GraphQL Playground and Tools

📖 Scenario: You are working with a GraphQL API for a simple book store. You want to explore the API using GraphQL Playground and understand how to use its tools to write queries and see results.

🎯 Goal: Learn to set up and use GraphQL Playground to write queries, use variables, and explore schema documentation.

📋 What You'll Learn

Open GraphQL Playground connected to the book store API endpoint

Write a query to fetch book titles and authors

Add variables to the query to filter books by genre

Use the documentation explorer to find available queries and types

💡 Why This Matters

🌍 Real World

GraphQL Playground is a tool developers use to explore and test GraphQL APIs quickly without writing code in an app.

💼 Career

Knowing how to use GraphQL Playground helps developers understand API capabilities and speeds up backend and frontend development.

1

Set up GraphQL Playground with API endpoint

Open GraphQL Playground and set the API endpoint URL to https://example.com/graphql in the URL bar.

GraphQL

# Set the API endpoint URL to https://example.com/graphql
# Your code here

Hint

Look for the URL input at the top of GraphQL Playground and enter the exact URL https://example.com/graphql.

2

Write a query to fetch book titles and authors

In the query editor, write a GraphQL query named GetBooks that fetches the title and author fields from books.

GraphQL

# Write a query named GetBooks to fetch title and author from books
# Your code here

Hint

Use the query keyword followed by the query name GetBooks. Inside, request books with title and author fields.

3

Add variables to filter books by genre

Modify the GetBooks query to accept a variable $genre of type String. Use this variable to filter books by genre with an argument genre: $genre.

GraphQL

# Modify GetBooks query to accept $genre variable and filter books by genre
# Your code here

Hint

Declare the variable $genre in parentheses after the query name with type String. Pass it as an argument to books.

4

Use documentation explorer to find available queries

Open the documentation explorer panel in GraphQL Playground. Find and list the names of at least two queries available in the schema.

GraphQL

# Open documentation explorer and find two query names
# Your code here

Hint

Click the Docs tab on the right side in GraphQL Playground. Look under the Query type to see available queries like books and bookById.

Practice

1. What is the main purpose of GraphQL Playground?

easy

A. To write and test GraphQL queries easily without extra setup

B. To store large amounts of data permanently

C. To replace SQL databases with a new storage system

D. To create user interfaces for mobile apps

Solution

1. Step 1: Understand GraphQL Playground's role

   GraphQL Playground is a tool designed to help users write and test GraphQL queries interactively.

2. Step 2: Compare options with this role

   Only To write and test GraphQL queries easily without extra setup describes this purpose correctly; others describe unrelated functions.

3. Final Answer:

   To write and test GraphQL queries easily without extra setup -> Option A

4. Quick Check:

   GraphQL Playground = Query testing tool [OK]

Hint: Think: Playground means a place to try things out [OK]

Common Mistakes:

• Confusing Playground with database storage
• Thinking it builds app interfaces
• Assuming it replaces databases

2. Which of the following is the correct way to start a query in GraphQL Playground?

easy

A. SELECT * FROM user

B. query { user { id name } }

C. { user id name }

D. GET user { id, name }

Solution

1. Step 1: Recall GraphQL query syntax

   GraphQL queries start with the keyword query followed by the selection set in braces.

2. Step 2: Check each option's syntax

   query { user { id name } } uses correct GraphQL syntax. Options B and D use SQL or HTTP-like syntax, and C misses the query keyword and braces.

3. Final Answer:

   query { user { id name } } -> Option B

4. Quick Check:

   GraphQL queries start with 'query' [OK]

Hint: GraphQL queries start with 'query' keyword and braces [OK]

Common Mistakes:

• Using SQL syntax instead of GraphQL
• Omitting the 'query' keyword
• Missing braces around fields

3. Given this GraphQL query in Playground:

query { book(id: "1") { title author } }

What will the result look like if the book with id "1" has title "GraphQL Guide" and author "Anna"?

medium

A. { "book": { "title": "GraphQL Guide", "author": "Anna" } }

B. { "data": { "book": ["GraphQL Guide", "Anna"] } }

C. { "data": { "book": { "title": "GraphQL Guide", "author": "Anna" } } }

D. { "data": { "book": { "name": "GraphQL Guide", "writer": "Anna" } } }

Solution

1. Step 1: Understand GraphQL response format

   GraphQL responses wrap requested data inside a top-level "data" object matching the query structure.

2. Step 2: Match query fields with response

   The query asks for title and author fields of book. { "data": { "book": { "title": "GraphQL Guide", "author": "Anna" } } } matches this exactly with correct field names and structure.

3. Final Answer:

   { "data": { "book": { "title": "GraphQL Guide", "author": "Anna" } } } -> Option C

4. Quick Check:

   GraphQL response = data wrapper + requested fields [OK]

Hint: GraphQL results always wrap data inside a 'data' object [OK]

Common Mistakes:

• Omitting the 'data' wrapper in response
• Using wrong field names in response
• Returning arrays instead of objects

4. You wrote this query in GraphQL Playground:

query { user(id: 5) { name email } }

But you get an error. What is the likely cause?

medium

A. GraphQL Playground does not support arguments

B. The query keyword is missing

C. Field names must be uppercase

D. The id argument should be a string, so it needs quotes

Solution

1. Step 1: Check argument types in GraphQL

   GraphQL requires string arguments to be in quotes. Here, id is likely a string but given without quotes.

2. Step 2: Verify other options

   The query keyword is present, field names are case-sensitive but lowercase is valid, and Playground supports arguments. So only The id argument should be a string, so it needs quotes explains the error.

3. Final Answer:

   The id argument should be a string, so it needs quotes -> Option D

4. Quick Check:

   String args need quotes in GraphQL [OK]

Hint: Put quotes around string arguments in queries [OK]

Common Mistakes:

• Leaving string arguments unquoted
• Assuming Playground lacks argument support
• Changing field name case incorrectly

5. You want to explore a new GraphQL API using Playground. Which feature helps you see all available types and fields without writing a query?

hard

A. The Schema Explorer sidebar showing types and fields

B. The Query History panel listing past queries

C. The Response Formatter that beautifies output

D. The Variable Editor for setting query variables

Solution

1. Step 1: Identify features for schema exploration

   GraphQL Playground includes a Schema Explorer sidebar that lists all types, queries, mutations, and fields available in the API.

2. Step 2: Compare other options

   Query History shows past queries, Response Formatter beautifies output, Variable Editor manages variables. Only Schema Explorer shows API schema details.

3. Final Answer:

   The Schema Explorer sidebar showing types and fields -> Option A

4. Quick Check:

   Schema Explorer = view API types and fields [OK]

Hint: Use Schema Explorer to browse API structure easily [OK]

Common Mistakes:

• Confusing Query History with schema browsing
• Thinking Response Formatter shows schema
• Assuming Variable Editor lists fields