Iterators for Custom Types

If a custom type is iterable, the for loop can be used to iterate through its items in sequence.

In order to use a for statement, a type iterator must be registered for the custom type in question.

Engine::register_iterator<T> allows registration of a type iterator for any type that implements IntoIterator:

fn main() {
// Custom type
#[derive(Debug, Clone)]
struct TestStruct { fields: Vec<i64> }

// Implement 'IntoIterator' trait
impl IntoIterator<Item = i64> for TestStruct {
    type Item = i64;
    type IntoIter = std::vec::IntoIter<Self::Item>;

    fn into_iter(self) -> Self::IntoIter {

      .register_fn("new_ts", || TestStruct { fields: vec![1, 2, 3, 42] })
      .register_iterator::<TestStruct>();         // register type iterator

With a type iterator registered, the custom type can be iterated through:

fn main() {
let ts = new_ts();

// Use 'for' statement to loop through items in 'ts'
for value in ts {