常量
声明,延迟计算的常量
声明一个延迟计算的HashMap
常量。 这个HashMap
会执行一次,在之后,会存储在全局的静态引用(PRIVILEGES)背后。
#[macro_use] extern crate lazy_static; use std::collections::HashMap; lazy_static! { static ref PRIVILEGES: HashMap<&'static str, Vec<&'static str>> = { let mut map = HashMap::new(); map.insert("James", vec!["user", "admin"]); map.insert("Jim", vec!["user"]); map }; } fn show_access(name: &str) { let access = PRIVILEGES.get(name); println!("{}: {:?}", name, access); } fn main() { let access = PRIVILEGES.get("James"); println!("James: {:?}", access); show_access("Jim"); }