1  #[derive(Debug, PartialEq, Copy, Clone)]
 2  enum ShirtColor {
 3      Red,
 4      Blue,
 5  }
 6  
 7  struct Inventory {
 8      shirts: Vec<ShirtColor>,
 9  }
10  
11  impl Inventory {
12      fn giveaway(&self, user_preference: Option<ShirtColor>) -> ShirtColor {
13          user_preference.unwrap_or_else(|| self.most_stocked())
14      }
15  
16      fn most_stocked(&self) -> ShirtColor {
17          let mut num_red = 0;
18          let mut num_blue = 0;
19  
20          for color in &self.shirts {
21              match color {
22                  ShirtColor::Red => num_red += 1,
23                  ShirtColor::Blue => num_blue += 1,
24              }
25          }
26          if num_red > num_blue {
27              ShirtColor::Red
28          } else {
29              ShirtColor::Blue
30          }
31      }
32  }
33  
34  fn main() {
35      let store = Inventory {
36          shirts: vec![ShirtColor::Blue, ShirtColor::Red, ShirtColor::Blue],
37      };
38  
39      let user_pref1 = Some(ShirtColor::Red);
40      let giveaway1 = store.giveaway(user_pref1);
41      println!(
42          "The user with preference {:?} gets {:?}",
43          user_pref1, giveaway1
44      );
45  
46      let user_pref2 = None;
47      let giveaway2 = store.giveaway(user_pref2);
48      println!(
49          "The user with preference {:?} gets {:?}",
50          user_pref2, giveaway2
51      );
52  }