GET and POST requests in Flutter - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a GET request in Flutter?

A GET request asks a server to send data. It is like asking for information without changing anything on the server.

beginner

What does a POST request do?

A POST request sends data to the server to create or update something. It is like submitting a form or sending a message.

beginner

Which Flutter package is commonly used for making HTTP GET and POST requests?

The 'http' package is commonly used to make GET and POST requests in Flutter apps.

intermediate

How do you handle the response of a GET request in Flutter?

You wait for the response asynchronously, then check the status code and use the response body data to update your app.

intermediate

Why should POST request data be sent in the request body?

POST request data is sent in the body because it can be large or complex, like JSON, and it changes server data unlike GET which sends data in the URL.

Which HTTP method is used to retrieve data without changing it?

A GET

B POST

C PUT

D DELETE

GET requests are used to fetch data without modifying it.

In Flutter, which package do you import to make HTTP requests?

A http

B flutter_http

C networking

D dio

The 'http' package is the standard package for HTTP requests in Flutter.

Where is data sent in a POST request?

A In the URL

B In the request headers

C In the request body

D In the response

POST request data is sent in the request body.

What does a status code 200 mean after a GET request?

A Request failed

B Unauthorized

C Server error

D Request succeeded

Status code 200 means the request was successful.

Which keyword helps you wait for an HTTP response in Flutter?

A async

B await

C then

D future

The 'await' keyword pauses code until the HTTP response arrives.

Explain the difference between GET and POST requests in Flutter.

Think about when you just want to see data versus when you want to send or save data.

Describe how you would make a simple GET request in Flutter using the http package.

Imagine you are asking a friend for information and waiting for their reply.

Practice

1. What is the main purpose of a GET request in Flutter when using the http package?

easy

A. To send data to a server to create or update something

B. To delete data from a server

C. To fetch data from a server without changing it

D. To authenticate a user

Solution

1. Step 1: Understand GET request purpose

   GET requests are used to retrieve or fetch data from a server without modifying it.

2. Step 2: Compare with other request types

   POST requests send data to create or update, DELETE removes data, and authentication is separate.

3. Final Answer:

   To fetch data from a server without changing it -> Option C

4. Quick Check:

   GET = fetch data [OK]

Hint: GET fetches data, POST sends data [OK]

Common Mistakes:

• Confusing GET with POST requests
• Thinking GET modifies server data
• Mixing GET with DELETE or authentication

2. Which of the following is the correct syntax to make a POST request using the http package in Flutter?

easy

A. http.post(Uri.parse(url), body: {"key": "value"});

B. http.get(Uri.parse(url), body: {"key": "value"});

C. http.post(url, {"key": "value"});

D. http.sendPost(Uri.parse(url), body: {"key": "value"});

Solution

1. Step 1: Identify correct method and parameters

   The http.post method requires a Uri object and an optional body map for data.

2. Step 2: Check syntax correctness

   http.post(Uri.parse(url), body: {"key": "value"}); uses Uri.parse(url) and passes body correctly. Others use wrong methods or parameters.

3. Final Answer:

   http.post(Uri.parse(url), body: {"key": "value"}); -> Option A

4. Quick Check:

   POST syntax = http.post(Uri.parse(url), body) [OK]

Hint: Use Uri.parse() and http.post() with body map [OK]

Common Mistakes:

• Passing URL as string instead of Uri
• Using http.get instead of http.post for POST
• Wrong method name like sendPost

3. What will be the output of this Flutter code snippet using the http package?

var response = await http.get(Uri.parse('https://jsonplaceholder.typicode.com/posts/1'));
print(response.statusCode);
print(response.body.contains('userId'));

medium

A. 200 and false

B. 404 and false

C. 500 and false

D. 200 and true

Solution

1. Step 1: Understand the GET request URL

   The URL points to a valid post resource, so the server should respond with status 200 (OK).

2. Step 2: Check response body content

   The JSON response includes a 'userId' field, so response.body.contains('userId') returns true.

3. Final Answer:

   200 and true -> Option D

4. Quick Check:

   Status 200 and body contains 'userId' = true [OK]

Hint: Valid URL returns 200 and expected JSON content [OK]

Common Mistakes:

• Assuming 404 for valid URL
• Not checking response body content
• Confusing status codes

4. Identify the error in this Flutter code that tries to send a POST request:

var response = await http.post('https://example.com/api', body: {"name": "John"});
print(response.statusCode);

medium

A. Body should be a JSON string, not a map

B. URL should be wrapped with Uri.parse()

C. http.post cannot be awaited

D. Missing headers for content type

Solution

1. Step 1: Check URL parameter type

   The http.post method requires the URL as a Uri object, not a plain string.

2. Step 2: Confirm correct usage

   Wrapping the URL string with Uri.parse() fixes the error. Other options are not mandatory errors here.

3. Final Answer:

   URL should be wrapped with Uri.parse() -> Option B

4. Quick Check:

   URL must be Uri.parse(string) [OK]

Hint: Always wrap URL string with Uri.parse() [OK]

Common Mistakes:

• Passing URL as plain string
• Assuming body must be JSON string always
• Forgetting to await async calls

5. You want to send a POST request with JSON data and receive a JSON response in Flutter. Which code snippet correctly handles this scenario using the http package?

hard

A. var response = await http.post(Uri.parse(url), headers: {"Content-Type": "application/json"}, body: jsonEncode({"name": "Alice"}));
var data = jsonDecode(response.body);

B. var response = await http.post(Uri.parse(url), body: {"name": "Alice"});
var data = response.body;

C. var response = await http.get(Uri.parse(url), headers: {"Content-Type": "application/json"});
var data = jsonDecode(response.body);

D. var response = await http.post(url, body: jsonEncode({"name": "Alice"}));
var data = jsonDecode(response.body);

Solution

1. Step 1: Set headers and encode body correctly

   To send JSON data, set header "Content-Type" to "application/json" and encode body with jsonEncode.

2. Step 2: Parse JSON response properly

   Use jsonDecode on response.body to convert JSON string to Dart object.

3. Step 3: Check URL parameter type

   URL must be wrapped with Uri.parse() for correct request.

4. Final Answer:

   Use http.post with Uri.parse, headers, jsonEncode body, and jsonDecode response -> Option A

5. Quick Check:

   POST JSON = headers + jsonEncode + jsonDecode [OK]

Hint: Use headers and jsonEncode for POST JSON, decode response [OK]

Common Mistakes:

• Not setting Content-Type header
• Passing body as map without encoding
• Using http.get instead of post for sending data
• Passing URL as string without Uri.parse