Code shared from the Rust Playground

playground.rs

fn main() {
    let filter = "Joh";
    let names = vec!["John", "Jane", "Johnny"];
    let lowered_filter = filter.to_lowercase();
    let filterNames = |x: &&str| -> bool {
        x.to_lowercase().contains(&lowered_filter)
    };    
    let filtered: Vec<&str> = names.iter().cloned().filter(filterNames).collect();
    
    println!("List {:?}", filtered);
}