Hive for NoSQL storage in Flutter - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a Hive box named 'settings'.

Flutter

var box = await Hive.[1]('settings');

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

AdeleteBox

BcloseBox

CopenBox

DcreateBox

Attempts:

3 left

💡 Hint

Common Mistakes

Using closeBox instead of openBox

Trying to createBox which doesn't exist

Use openBox to open or create a box in Hive.

2fill in blank

medium

Complete the code to add a value 'dark' with key 'theme' to the box.

Flutter

await box.[1]('theme', 'dark');

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

Aget

Bput

Cdelete

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using get instead of put

Using delete or clear which remove data

Use put to store a value with a key in Hive.

3fill in blank

hard

Fix the error in the code to read the value for key 'username' from the box.

Flutter

var username = box.[1]('username');

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

Aput

Bclear

Cdelete

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using put instead of get

Using delete or clear which remove data

Use get to read a value by key from Hive box.

4fill in blank

hard

Fill both blanks to delete the key 'token' and then close the box.

Flutter

await box.[1]('token');
await box.[2]();

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

Adelete

Bclose

Cput

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using put or get instead of delete

Not closing the box properly

Use delete to remove a key and close to close the box.

5fill in blank

hard

Fill all three blanks to create a map of all keys and values where values are not null.

Flutter

var allData = {for (var key in box.[1]) if (box.[3](key) != null) key: box.[2](key)};

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

Akeys

Bget

Dvalues

Attempts:

3 left

💡 Hint

Common Mistakes

Using values instead of keys for iteration

Using wrong method to get values

Use keys to iterate keys, and get to get values.

Practice

1. What is the main purpose of Hive in Flutter apps?

easy

A. To handle network requests

B. To create user interfaces

C. To store data locally in a simple way

D. To manage app navigation

Solution

1. Step 1: Understand Hive's role

   Hive is designed as a local storage solution for Flutter apps, meaning it saves data on the device.

2. Step 2: Compare with other options

   Creating UI, handling network, and navigation are unrelated to data storage, so they are incorrect.

3. Final Answer:

   To store data locally in a simple way -> Option C

4. Quick Check:

   Hive = local data storage [OK]

Hint: Hive is for local data storage, not UI or network [OK]

Common Mistakes:

• Confusing Hive with UI or network libraries
• Thinking Hive manages app navigation
• Assuming Hive is for remote databases

2. Which of the following is the correct way to open a Hive box named settings?

easy

A. var box = await Hive.openBox('settings');

B. var box = Hive.openBox('settings');

C. var box = Hive.box('settings');

D. var box = await Hive.box('settings');

Solution

1. Step 1: Recall Hive box opening syntax

   Opening a box is asynchronous and requires await Hive.openBox('boxName').

2. Step 2: Check options for async and method

   var box = await Hive.openBox('settings'); uses await and openBox correctly. Omitting await on Hive.openBox('settings') returns a Future. Hive.box('settings') only accesses an already opened box synchronously, and awaiting Hive.box('settings') is incorrect as it is synchronous.

3. Final Answer:

   var box = await Hive.openBox('settings'); -> Option A

4. Quick Check:

   Open box = await Hive.openBox() [OK]

Hint: Use await with openBox to open Hive boxes [OK]

Common Mistakes:

• Forgetting await when opening a box
• Using Hive.box() before opening the box
• Awaiting Hive.box() which is synchronous

3. Given the following code, what will be printed?

var box = await Hive.openBox('favorites');
await box.put('color', 'blue');
print(box.get('color'));

medium

A. null

B. blue

C. color

D. Error

Solution

1. Step 1: Understand put and get methods

   The put method saves a value with a key, here 'color' = 'blue'. The get method retrieves the value for the key.

2. Step 2: Trace the code output

   After putting 'blue' under 'color', box.get('color') returns 'blue', which is printed.

3. Final Answer:

   blue -> Option B

4. Quick Check:

   Put then get returns stored value [OK]

Hint: put stores, get retrieves the value by key [OK]

Common Mistakes:

• Expecting get to return the key instead of value
• Thinking put is asynchronous but get is not
• Assuming get returns null if key exists

4. What is wrong with this code snippet?

var box = Hive.openBox('settings');
await box.put('theme', 'dark');

medium

A. put method does not exist

B. Cannot use await inside async function

C. Box name must be an integer

D. Missing await before Hive.openBox

Solution

1. Step 1: Check box opening syntax

   Hive.openBox is asynchronous and must be awaited to get the box instance.

2. Step 2: Identify error cause

   Without await, box is a Future, so calling put on it causes an error.

3. Final Answer:

   Missing await before Hive.openBox -> Option D

4. Quick Check:

   Always await openBox before using box [OK]

Hint: Always await openBox before using the box object [OK]

Common Mistakes:

• Not awaiting openBox causing Future errors
• Thinking box name must be a number
• Misusing await outside async functions

5. You want to save a list of favorite items in Hive under the key favorites. Which code correctly saves and retrieves this list?

hard

A. await box.put('favorites', ['apple', 'banana']);
var list = box.get('favorites');

B. await box.put(['favorites'], 'apple, banana');
var list = box.get(['favorites']);

C. box.put('favorites', ['apple', 'banana']);
var list = await box.get('favorites');

D. box.put('favorites', 'apple, banana');
var list = box.get('favorites');

Solution

1. Step 1: Check correct put syntax for list

   Use await box.put(key, value) with key as string and value as list to save data.

2. Step 2: Retrieve list correctly

   Use box.get(key) synchronously to get saved list. Await is not needed for get.

3. Final Answer:

   await box.put('favorites', ['apple', 'banana']); var list = box.get('favorites'); -> Option A

4. Quick Check:

   Put list with await, get list without await [OK]

Hint: Put with await, get without await for Hive data [OK]

Common Mistakes:

• Using list as key instead of string
• Awaiting get method which is synchronous
• Saving list as string instead of list