Dio package for advanced HTTP in Flutter - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Dio instance for HTTP requests.

Flutter

final dio = Dio([1]);

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

AOptions()

BBaseOptions()

CRequestOptions()

DHttpClient()

Attempts:

3 left

💡 Hint

Common Mistakes

Using HttpClient instead of BaseOptions.

Trying to pass Options directly to Dio constructor.

The Dio constructor accepts BaseOptions to configure base URL, headers, and more.

2fill in blank

medium

Complete the code to make a GET request using Dio.

Flutter

final response = await dio.[1]('https://example.com/data');

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

Aget

Bput

Cpost

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using post instead of get for fetching data.

Confusing put or delete with get.

Use get method to fetch data from a URL with Dio.

3fill in blank

hard

Fix the error in the code to add a request interceptor in Dio.

Flutter

dio.interceptors.add(InterceptorsWrapper(onRequest: (options, handler) async {
  options.headers['Authorization'] = 'Bearer [1]';
  return handler.next(options);
}));

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

A12345

Bawait getToken()

Cnull

Dtoken

Attempts:

3 left

💡 Hint

Common Mistakes

Using an async call directly inside header assignment.

Assigning null or a number instead of a string token.

The options.headers expects a string token. Use a variable token holding the token string.

4fill in blank

hard

Fill both blanks to create a POST request with JSON data using Dio.

Flutter

final response = await dio.[1]('https://example.com/login', data: [2]);

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

Apost

B{'username': 'user', 'password': 'pass'}

C[1, 2, 3]

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using get method instead of post.

Passing a list instead of a map for JSON data.

Use post method to send data. The data parameter accepts a map for JSON body.

5fill in blank

hard

Fill all three blanks to handle Dio errors with try-catch.

Flutter

try {
  final response = await dio.[1]('https://example.com/data');
  print(response.[2]);
} on DioException catch ([3]) {
  print('Request failed');
}

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

Aget

Bdata

Ce

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong HTTP method.

Accessing response incorrectly.

Using wrong variable name in catch.

Use get to fetch data. Access response body with data. Catch error with variable e.

Practice

1. What is the primary purpose of the Dio package in Flutter?

easy

A. To manage local databases

B. To create UI animations

C. To make HTTP requests easily with advanced features

D. To handle user input gestures

Solution

1. Step 1: Understand Dio's role

   Dio is designed as an HTTP client to simplify network calls in Flutter apps.

2. Step 2: Compare with other options

   Other options like UI animations or database management are unrelated to Dio's purpose.

3. Final Answer:

   To make HTTP requests easily with advanced features -> Option C

4. Quick Check:

   Dio = HTTP client [OK]

Hint: Dio is all about HTTP requests, not UI or storage [OK]

Common Mistakes:

• Confusing Dio with UI or database packages
• Thinking Dio handles gestures
• Assuming Dio is for local storage

2. Which of the following is the correct way to create a Dio instance with a base URL of 'https://api.example.com'?

easy

A. var dio = Dio(BaseOptions(baseUrl: 'https://api.example.com'));

B. var dio = Dio('https://api.example.com');

C. var dio = Dio().setBaseUrl('https://api.example.com');

D. var dio = Dio(baseUrl: 'https://api.example.com');

Solution

1. Step 1: Check Dio instance creation syntax

   Dio requires BaseOptions to set baseUrl during initialization.

2. Step 2: Validate each option

   var dio = Dio(BaseOptions(baseUrl: 'https://api.example.com')); uses BaseOptions correctly; others misuse constructor or methods.

3. Final Answer:

   var dio = Dio(BaseOptions(baseUrl: 'https://api.example.com')); -> Option A

4. Quick Check:

   BaseOptions sets baseUrl in Dio [OK]

Hint: Use BaseOptions to set baseUrl when creating Dio [OK]

Common Mistakes:

• Passing URL directly to Dio constructor
• Using nonexistent setBaseUrl method
• Setting baseUrl as a direct parameter

3. Given the code snippet:

var dio = Dio();
var response = await dio.get('https://jsonplaceholder.typicode.com/posts/1');
print(response.data['id']);

What will be printed?

medium

A. 1

B. null

C. An error message

D. The entire JSON response

Solution

1. Step 1: Understand the GET request

   The code fetches post with id 1 from the API.

2. Step 2: Access response data

   response.data['id'] accesses the 'id' field, which is 1.

3. Final Answer:

   1 -> Option A

4. Quick Check:

   response.data['id'] = 1 [OK]

Hint: Access response.data keys to get JSON fields [OK]

Common Mistakes:

• Expecting entire JSON instead of specific field
• Not awaiting the async call
• Using wrong key to access data

4. Identify the error in this Dio request code:

var dio = Dio();
var response = dio.get('https://api.example.com/data');
print(response.data);

medium

A. Dio instance not created properly

B. Incorrect URL format

C. response.data is not a valid property

D. Missing await keyword for async call

Solution

1. Step 1: Check async call usage

   dio.get returns a Future; it must be awaited to get response.

2. Step 2: Identify missing await

   Code lacks await, so response is a Future, not the actual response object.

3. Final Answer:

   Missing await keyword for async call -> Option D

4. Quick Check:

   Async calls need await [OK]

Hint: Always await async Dio calls to get response [OK]

Common Mistakes:

• Forgetting await on async requests
• Assuming dio.get is synchronous
• Trying to access data on Future object

5. How can you add a custom header 'Authorization: Bearer token123' to all requests made by a Dio instance?

hard

A. Add headers directly in each get/post call only

B. Set headers in BaseOptions when creating Dio instance

C. Use dio.addHeader('Authorization', 'Bearer token123') method

D. Modify the response interceptor to add headers

Solution

1. Step 1: Understand global headers setup

   Headers for all requests are set in BaseOptions.headers when creating Dio.

2. Step 2: Evaluate options

   Setting headers in BaseOptions applies them globally to all requests; adding them per get/post call is request-specific; there is no addHeader method on Dio; response interceptors handle responses, not request headers.

3. Final Answer:

   Set headers in BaseOptions when creating Dio instance -> Option B

4. Quick Check:

   Global headers = BaseOptions.headers [OK]

Hint: Use BaseOptions.headers for global request headers [OK]

Common Mistakes:

• Trying to add headers via nonexistent methods
• Setting headers only per request instead of globally
• Confusing response interceptors with request headers