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Map and Collect

Map: The map function is used to transform elements of an iterator. It takes a closure and applies this closure to each element of the iterator, producing a new iterator with the transformed elements.

• Takes a closure
• Applies transformation lazily
• Returns another iterator

Collect: The collect function is used to transform an iterator into a collection, such as a Vec, HashMap, or HashSet. It consumes the iterator and returns the new collection.

• Consumes iterator
• Produces concrete collection

fn main() {
    let numbers = vec![1, 2, 3, 4, 5];

    let doubled: Vec<i32> = numbers.iter().map(|x| x * 2).collect();

    println!("{:?}", doubled);
}

• map() does NOT execute immediately
• It returns a lazy iterator
• Nothing happens until you consume it

fn main() {
    let names = vec!["rachel", "ross", "joey"];

    let upper: Vec<String> = names
        .iter()
        .map(|name| name.to_uppercase())
        .collect();

    println!("{:?}", upper);
}

Map + Filter

fn main() {
    let numbers = vec![1, 2, 3, 4, 5];

    let result: Vec<i32> = numbers
        .iter()
        .map(|x| x * 2)
        .filter(|x| *x > 5)
        .collect();

    println!("{:?}", result);
}

#map #collectVer 2.0.22