rustHow to pass a Rust HashMap as an argument?

Passing a Rust HashMap as an argument is done by using the & operator. This operator allows the HashMap to be passed by reference, meaning that the original HashMap is not copied.

Example code

fn print_map(map: &HashMap<String, i32>) {
    for (key, value) in map {
        println!("{}: {}", key, value);
    }
}

fn main() {
    let mut map = HashMap::new();
    map.insert("one".to_string(), 1);
    map.insert("two".to_string(), 2);
    print_map(&map);
}

Output example

one: 1
two: 2

Code explanation

• fn print_map(map: &HashMap<String, i32>): This is the function declaration, which takes a reference to a HashMap as an argument.
• for (key, value) in map: This loop iterates over the HashMap, allowing each key-value pair to be accessed.
• println!("{}: {}", key, value);: This prints the key-value pair to the console.
• let mut map = HashMap::new();: This creates a new, empty HashMap.
• map.insert("one".to_string(), 1);: This inserts a key-value pair into the HashMap.
• print_map(&map);: This passes the HashMap to the print_map function.

Helpful links

• Rust Documentation - HashMap
• Rust Documentation - Reference

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