Iterator Over Collections

Note: No official YouTube video yet, but our Rust Developer Bootcamp covers this topic!

Additional Resources

• Make iterators 10X better with itertools

Exercises

Iterating immutably

//  Make the code compile by filling in the `???`s

fn main() {
    let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];

    let mut my_iterable_fav_fruits = ???;   // TODO: Step 1

    assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 2
    assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 3
    assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
    assert_eq!(my_iterable_fav_fruits.next(), ???);     // TODO: Step 4
}

fn main() {
  let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];

  let mut my_iterable_fav_fruits = my_fav_fruits.iter();

  assert_eq!(my_iterable_fav_fruits.next(), Some(&"banana"));
  assert_eq!(my_iterable_fav_fruits.next(), Some(&"custard apple"));
  assert_eq!(my_iterable_fav_fruits.next(), Some(&"avocado"));
  assert_eq!(my_iterable_fav_fruits.next(), Some(&"peach"));
  assert_eq!(my_iterable_fav_fruits.next(), Some(&"raspberry"));
  assert_eq!(my_iterable_fav_fruits.next(), None);
}

Iterating mutably

// Make the code compile by only modifying the loop.

fn main() {
    let mut nums = [0, 1, 2, 3, 4];
    let odd_nums = [1, 3, 5, 7, 9];
    for num in nums.iter() {
        *num = 2 * *num + 1;
    }
    assert_eq!(nums, odd_nums)
}

fn main() {
  let mut nums = [0, 1, 2, 3, 4];
  let odd_nums = [1, 3, 5, 7, 9];
  for num in nums.iter_mut() {
      *num = 2 * *num + 1;
  }
  assert_eq!(nums, odd_nums)
}

Hashmaps

// Fix the code to make it compile.

use std::collections::HashMap;

fn main() {
    // marks scored out of 50
    let mut marks = HashMap::from([("Harry", 40.0), ("Hermoine", 50.0), ("Ron", 35.5)]);
    // convert marks into percentage
    for (_, marks) in marks {
        *marks = (*marks * 100.0) / 50.0;
    }
    marks.for_each(|(student, marks)| println!("{student} scored {marks}%"));
}

use std::collections::HashMap;

fn main() {
  // marks scored out of 50
  let mut marks = HashMap::from([("Harry", 40.0), ("Hermoine", 50.0), ("Ron", 35.5)]);
  // convert marks into percentage
  for (_, marks) in marks.iter_mut() {
      *marks = (*marks * 100.0) / 50.0;
  }
  marks.iter().for_each(|(student, marks)| println!("{student} scored {marks}%"));
}