hashmap_to_hashmap/
lib.rs

1use std::collections::HashMap;
2use std::hash::Hash;
3
4pub trait Map<PK: Hash+Eq, PV, NK: Hash+Eq, NV, FK: Fn(&PK, &PV)->NK, FV: Fn(&PK, &PV)->NV> {
5    fn map(self, key_func: FK, value_func: FV) -> HashMap<NK, NV>;
6}
7
8impl <PK: Hash+Eq, PV, NK: Hash+Eq, NV, FK: Fn(&PK, &PV)->NK, FV: Fn(&PK, &PV)->NV> Map<PK, PV, NK, NV, FK, FV> for HashMap<PK, PV> {
9    fn map(self, key_func: FK, value_func: FV) -> HashMap<NK, NV> {
10        let mut new_map: HashMap<NK, NV> = HashMap::new();
11        for (key, value) in self {
12            new_map.insert(key_func(&key, &value), value_func(&key, &value));
13        }
14        new_map
15    }
16}
17
18#[cfg(test)]
19mod tests {
20    use super::*;
21    use std::collections::HashMap;
22
23    struct Person<'s> {
24        id: i32,
25        first_name: &'s str,
26        last_name: &'s str,
27    }
28
29    #[test]
30    fn it_works() {
31        let brad = Person {
32            id: 1,
33            first_name: "Brad",
34            last_name: "Urani",
35        };
36        let susan = Person {
37            id: 2,
38            first_name: "Susan",
39            last_name: "Urani",
40        };
41        let mut h: HashMap<i32, Person> = HashMap::new();
42        h.insert(12, brad);
43        h.insert(29, susan);
44
45        let mut expected = HashMap::new();
46        expected.insert(1, "12-Brad Urani");
47        expected.insert(2, "29-Susan Urani");
48
49        let new_map = h.map(|_, v| v.id,
50                            |k, v| k.to_string() + &"-" + &v.first_name + &" " + &v.last_name);
51        assert_eq!(new_map.get(&1).unwrap(), expected.get(&1).unwrap());
52        assert_eq!(new_map.get(&2).unwrap(), expected.get(&2).unwrap());
53    }
54
55}
hashmap_to_hashmap/lib.rs

hashmap_to_hashmap/
lib.rs
