rust - How can I return something from HashMap.get’s None case? -

i'm wondering best practice handle none result in getting values hashmap. given have simple function:

pub fn get_value(&self, value: string) -> &string { 

one value hashmap unwrap:

my_map.get(&"hello".to_string()).unwrap() 

but don’t want panic if gets none. else can do?

match self.os_config.get(&value) {     some(val) => return &val,     none =>  //?? cannot return string::new().. temporal? } 

for starters, &string type should never exist in signature; should take more general &str. string owned string, while &str string slice. because string implements deref<target = str>, &string coerces &str.

when dealing hash map keys, should take &str rather &string, , should avoid taking string if need &str; don’t need consume string. can index hashmap<string, _> &str fine.

the type of string literal &'static str; &'static str quite happily coerce &'a str 'a, can quite happily use empty string literal on none branch. here’s result:

pub fn get_value(&self, value: &str) -> &str {     match self.os_config.get(value) {         some(val) => val,         none => "",     } } 

this can written using handy unwrap_or method:

pub fn get_value(&self, value: &str) -> &str {     self.os_config.get(value).unwrap_or("") } 

for reason, returning option<&str> perhaps not tedious; other places can add .unwrap_or("") if want to. of course, depends on desired semantics.