Why smart pointers are needed in Rust - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Box smart pointer.

Rust

let b = Box::new([1]);

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

Avec![1, 2, 3]

B&5

C5

DString::from("hello")

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a reference instead of a value.

Box::new takes ownership of a value, here the integer 5.

2fill in blank

medium

Complete the code to dereference a Box smart pointer.

Rust

let x = *[1];

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Ab

BBox

C&b

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Dereferencing a value or a reference instead of the Box variable.

Dereferencing a Box requires the variable holding the Box, here 'b'.

3fill in blank

hard

Fix the error in the code to use Rc smart pointer correctly.

Rust

use std::rc::Rc;
let a = Rc::new(5);
let b = Rc::clone(&[1]);

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Ab

Ba

C&a

DRc

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the wrong variable or a reference to the wrong type.

Rc::clone takes a reference to the Rc smart pointer variable, here &a.

4fill in blank

hard

Fill both blanks to create a RefCell and borrow mutably.

Rust

use std::cell::RefCell;
let data = RefCell::new([1]);
let mut val = data.[2]();

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A5

Bborrow_mut

Cborrow

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using borrow() instead of borrow_mut() for mutable access.

RefCell::new wraps a value, here 5, and borrow_mut() allows mutable access.

5fill in blank

hard

Fill all three blanks to create a smart pointer, borrow immutably, and print the value.

Rust

use std::rc::Rc;
let value = Rc::new([1]);
let borrowed = value.[2]();
println!("Value: {}", [3]);

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

A10

Bclone

Cborrowed

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong value or forgetting to clone Rc.

Rc::new wraps 5, clone() creates a new pointer, and borrowed is printed.