get - Return exact value in Rust Hashmap -

i can't find suitable way return exact value of key in hashmap in rust . existing get methods return in different format rather exact format.

there 2 basic methods of obtaining value given key: get() , get_mut(). use first 1 if want read value, , second 1 if need modify value:

fn get(&self, k: &q) -> option<&v> fn get_mut(&mut self, k: &q) -> option<&mut v> 

as can see signatures, both of these methods return option rather direct value. reason there may no value associated given key:

use std::collections::hashmap;  let mut map = hashmap::new(); map.insert(1, "a"); assert_eq!(map.get(&1), some(&"a")); // key exists assert_eq!(map.get(&2), none);       // key not exist 

if sure map contains given key, can use unwrap() value out of option:

assert_eq!(map.get(&1).unwrap(), &"a"); 

however, in general, better (and safer) consider case when key might not exist. example, may use pattern matching:

if let some(value) = map.get(&1) {     assert_eq!(value, &"a"); } else {     // there no value associated given key. }