minigrep_study/example/
closure.rs

1use std::{hash::Hash, collections::HashMap};
2
3pub struct Cacher<T,K,V>
4    where 
5        T: Fn(K) -> V,
6        K: Hash + Eq,
7        V: Copy,
8{
9    calculation: T,
10    value: HashMap<K,V>,
11}
12
13impl<T,K,V> Cacher<T,K,V> 
14    where 
15        T: Fn(K) -> V,
16        K: Hash + Eq + Copy,
17        V: Copy
18{
19    pub fn new(calculation: T) -> Cacher<T,K,V> {
20        let value: HashMap<K,V> = HashMap::new();
21        Cacher {
22            calculation,
23            value,
24        }
25    }
26
27    pub fn value(&mut self, arg: K) -> V {
28        // let tmp = arg.clone();
29        match self.value.get(&arg) {
30            Some(v) => *v,
31            None => {
32                let v = (self.calculation)(arg);
33                self.value.insert(arg, v);
34                v
35            },
36        }
37    }
38}
39
40#[cfg(test)]
41mod tests {
42    use super::*;
43
44    #[test]
45    fn call_with_different_values() {
46        let mut c = Cacher::new(|a| a);
47        let mut c2 = Cacher::new(|a: &str| a);
48
49        let v1 = c.value(1);
50        let s = "hello";
51        let v2 = c2.value(&s[..]);
52        let v3 = c.value(2);
53
54        assert_eq!(v1, 1);
55        assert_eq!(v2, "hello");
56        assert_eq!(v3, 2);
57    }
58}
59
minigrep_study/example/closure.rs

minigrep_study/example/
closure.rs
