Rust Vectors
Vectors
A vector is a resizable array. Unlike regular arrays, vectors can grow or shrink in size.
Creating a Vector
To create a vector, use the vec! macro:
Example
let fruits = vec!["apple", "banana", "orange"];
This creates a vector with three string elements.
Access Vector Elements
You can access values in a vector using index numbers (just like arrays):
Example
let fruits = vec!["apple", "banana", "orange"];
println!("First fruit: {}", fruits[0]);
Try it Yourself »
Change Vector Values
To change a value in the vector, refer to the index number and assign a new value.
Remember to make the vector mutable (using the mut keyword):
Example
let mut fruits = vec!["apple", "banana", "orange"];
fruits[0] = "grape";
println!("New first fruit: {}", fruits[0]);
Try it Yourself »
Add Elements to a Vector
You can add a new element to the end of a vector using the push()
method:
Example
let mut fruits = vec!["apple", "banana"];
fruits.push("cherry");
println!("{:?}", fruits); // ["apple", "banana", "cherry"]
Try it Yourself »
Remove Elements from a Vector
To remove the last element from a vector, use pop():
Example
let mut fruits = vec!["apple", "banana", "cherry"];
fruits.pop();
println!("{:?}", fruits); // ["apple", "banana"]
Try it Yourself »
Add or Remove Elements at a Specified Index
Rust vectors are designed to grow and shrink at the end, but you can also add or remove elements at the beginning or at a specified index.
Use insert() to add an item at a specified
index:
Example
Add "apple" to the beginning of the vector:
let mut fruits = vec!["banana", "orange"];
fruits.insert(0, "apple");
println!("{:?}", fruits); // ["apple", "banana", "orange"]
Try it Yourself »
Example
Add "apple" in the middle of the vector:
let mut fruits = vec!["banana", "orange"];
fruits.insert(1, "apple");
println!("{:?}", fruits); // ["banana", "apple", "orange"]
Try it Yourself »
Remove the First Item
Use remove() to remove an element from a specified
index:
Example
Remove the first item in the vector:
let mut fruits = vec!["apple", "banana", "orange"];
fruits.remove(0);
println!("{:?}", fruits); // ["banana", "orange"]
Try it Yourself »
Note: Adding or removing elements from the beginning is slower than at the end, because all the other elements have to shift positions.
Vector Length
You can find out how many elements there are in a vector using the .len() method:
Example
let fruits = vec!["apple", "banana", "cherry"];
println!("There are {} fruits.", fruits.len());
Try it Yourself »
Loop Through a Vector
Just like arrays, you can use a for loop to go through all the values in a vector:
Example
let fruits = vec!["apple", "banana", "orange"];
for fruit in &fruits {
println!("I like {}.", fruit);
}
Try it Yourself »
Note: Use &fruits to borrow the vector instead of moving it.
In Rust, borrowing means using a reference to a value instead of taking ownership of it.
When you loop through a vector without &, the values are moved out, and you can no longer use the vector.
But when you borrow the vector using &, you can still use it later in your program.
You can learn more about ownership in our chapters on Ownership and Borrowing and References.
