1 use lazy_static::lazy_static; 2 use regex::Regex; 3 4 lazy_static! { 5 static ref USERNAME: Regex = { 6 println!("Compiling username regex..."); 7 Regex::new("^[a-z0-9_-]{3,16}$").unwrap() 8 }; 9 } 10 main()11fn main() { 12 println!("Let's validate some usernames."); 13 validate("fergie"); 14 validate("will.i.am"); 15 } 16 validate(name: &str)17fn validate(name: &str) { 18 // The USERNAME regex is compiled lazily the first time its value is accessed. 19 println!("is_match({:?}): {}", name, USERNAME.is_match(name)); 20 } 21