How to chain iterators

Chain iterators by calling methods like .map(), .filter(), or .collect() sequentially on the iterator object to transform or process data in a single pass. This pattern is also used with async operations by chaining .await calls on futures, as seen in the trpl crate's page_title function.

let response_text = trpl::get(url).await.text().await;
Html::parse(&response_text)
    .select_first("title")
    .map(|title| title.inner_html());

For standard collections, chaining works similarly with synchronous iterators:

let numbers = vec![1, 2, 3, 4, 5];
let sum: i32 = numbers.iter()
    .filter(|&&x| x % 2 == 0)
    .map(|x| x * 2)
    .sum();

Chaining iterators means connecting multiple data processing steps together in a single line of code. Instead of writing separate loops to filter, transform, and sum data, you link these actions so the data flows through them one after another. Think of it like an assembly line where a product moves from one station to the next without stopping.