Iterators

Topics to cover

Iterator triat
next Method
iter, into_iter and iter_mut methods
collect method

Trait Definition:

pub trait Iterator {
    type Item;

    fn next(&mut self) -> Option<Self::Item>;

    // methods with default implementations elided
}

iter: The iter method produces an iterator over immutable references.

into_iter: If we want to create an iterator that takes ownership of source vector and returns owned values, we can call into_iter instead of iter.

iter_mut: Similarly, if we want to iterate over mutable references, we can call iter_mut instead of iter.

collect: This method consumes the iterator and collects the resulting values into a collection data type.

Methods that consume iterators

Consuming Adaptors : methods that call next
- Example: sum
```
  let total: i32 = v1_iter.sum();
```

Methods that produce iterators

Iterator Adaptors : they produce different iterators by changing some aspect of the original iterator
- Example: map
```
  let v1: Vec<i32> = vec![1, 2, 3];
  v1.iter().map(|x| x + 1);
```

Using Closures that Capture Their Environment

Many iterator adapters take closures as arguments

Example : filter

struct Shoe {
    size: u32,
    style: String,
}

fn shoes_in_size(shoes: Vec<Shoe>, shoe_size: u32) -> Vec<Shoe> {
    shoes.into_iter().filter(|s| s.size == shoe_size).collect()
}