Box pointer in Rust - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Box pointer holding the value 5.

Rust

let b = [1]::new(5);

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

AArc

BRc

CBox

DVec

Attempts:

3 left

💡 Hint

Common Mistakes

Using Vec instead of Box, which creates a vector, not a pointer.

Using Rc or Arc which are reference counted pointers, not simple boxes.

The Box::new function creates a Box pointer that owns the value on the heap.

2fill in blank

medium

Complete the code to dereference the Box pointer and print its value.

Rust

let b = Box::new(10);
println!("{}", *[1]);

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

ABox

Bb

C&b

Db.as_ref()

Attempts:

3 left

💡 Hint

Common Mistakes

Using &b which is a reference to the Box, not the value.

Using b.as_ref() which returns a reference, not the value itself.

Dereferencing the Box pointer b with *b accesses the value inside.

3fill in blank

hard

Fix the error in the code by completing the blank to create a Box pointer to a string.

Rust

let s = [1]::new(String::from("hello"));

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

AArc

BVec

CRc

DBox

Attempts:

3 left

💡 Hint

Common Mistakes

Using Vec which is a growable array, not a pointer.

Using Rc or Arc which are reference counted pointers.

Box::new correctly creates a Box pointer owning the String on the heap.

4fill in blank

hard

Fill both blanks to create a Box pointer to an integer and then dereference it to get the value.

Rust

let b = [1]::new(42);
let val = *[2];

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

ABox

Bb

CRc

DArc

Attempts:

3 left

💡 Hint

Common Mistakes

Using Rc or Arc instead of Box for simple ownership.

Dereferencing the type name instead of the variable.

First, Box::new creates the Box pointer. Then, dereferencing b with *b gets the value.

5fill in blank

hard

Fill all three blanks to create a Box pointer to a vector, push a value, and print the length.

Rust

let mut v = [1]::new(vec![1, 2, 3]);
v.[2](4);
println!("Length: {}", v.[3]());

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

ABox

Bpush

Clen

DVec

Attempts:

3 left

💡 Hint

Common Mistakes

Using Vec::new instead of Box::new to create the pointer.

Calling push or len on the Box pointer without dereferencing (but in Rust, Box auto-derefs).

Box::new creates the pointer to the vector. Then push adds an element, and len gets the vector length.