Vector: collection in Rust

Vector can be used to storing lists of values in Rust. It’s one of the collection that included in standard library in Rust.

Example usage: lines of text in a file or prices of items in a shopping cart.

What’s the different between vector and array

Vector is most similar to array in Rust, the different is array has a fixed length, while vector’s can grow!

How to create a Vector

This is how to create an empty vector in Rust

let v: Vec<i32> = Vec::new();

Vector always has a certain data type that can be written explicitly in Vector.

In real world, we can write directly Vector like this

let v = vec![1, 2, 3];

*the type annotation isn’t necessary

How to read a Vector

To read a vector, we can use index or get method.

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."),
}

Use &Vector[index]
Use Vector.get(index)

When the get method is passed an index that is outside the vector, it returns None without panicking. But using [] will return an error (crash).

Iterating a Vector

We can iterate through Vector

  let v = vec![100, 32, 57];
  for i in &v {
      println!("{}", i);
  }

Iterate and mutate a vector

let mut v = vec![100, 32, 57];
for i in &mut v {
    *i += 50;
}

How to update a Vector

We can use push method to add a new vector

let mut v = Vec::new();
v.push(5);
v.push(6);
v.push(7);
v.push(8);

Different type of values in Vector

To implement different type of values in Vector, we need to use enum

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),
  ];
}