src/doc/book/listings/ch13-functional-features/listing-13-01/src/main.rs

   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 }