Traits
std
convert
Description
Vectors allow you to store more than one value in a single data structure that puts all the values next to each other in memory. Vectors can only store values of the same type. They are useful when you have a list of items, such as the lines of text in a file or the prices of items in a shopping cart.
Creating a New Vector
fn main() {
let v: Vec<i32> = Vec::new();
}vec! macro
Rust can often infer the type of value you want to store in the Vector. For convenience one can also use the vec! macro.
fn main() {
let v = vec![1, 2, 3];
}Updating a Vector
fn main() {
let mut v = Vec::new();
v.push(5);
v.push(6);
v.push(7);
v.push(8);
}Dropping a Vector
Like other structs, vectors are freed when they go out of scope, along with the vector contents:
fn main() {
{
let v = vec![1, 2, 3, 4];
// do stuff with v
} // <- v goes out of scope and is freed here
}Read Vector elements
There are two ways to reference a value stored in a vector:
fn main() {
let v = vec![1, 2, 3, 4, 5];
let third: &i32 = &v[2];
println!("The third element is {}", third);
match v.get(2) {
Some(third) => println!("The third element is {}", third),
None => println!("There is no third element."),
}
}Using get together with match seems preferable, as trying to get non existant elements with method #1 will cause an `index out of bounds` panic:
fn main() {
let v = vec![1, 2, 3, 4, 5];
let does_not_exist = &v[100];
let does_not_exist = v.get(100);
}When the get method is passed an index that is outside the vector, it
returns None without panicking.
Iteration
Immutable references
fn main() {
let v = vec![100, 32, 57];
for i in &v {
println!("{}", i);
}
}Mutable references
fn main() {
let mut v = vec![100, 32, 57];
for i in &mut v {
*i += 50;
}
}Using Enums to store multiple types
fn main() {
enum SpreadsheetCell {
Int(i32),
Float(f64),
Text(String),
}
let row = vec![
SpreadsheetCell::Int(3),
SpreadsheetCell::Text(String::from("blue")),
SpreadsheetCell::Float(10.12),
];
}