rust解决嵌套——Option类型的map和and_then方法的使用

struct Peeled(String);
struct Choped(String);
struct Cooked(String);
// 削皮
fn peel(food: Option<String>) -> Option<Peeled> {
    match food {
        Some(food) => Some(Peeled(food)),
        None => None,
    }
}
// 切块
fn chop(peeled_food: Option<Peeled>) -> Option<Choped> {
    match peeled_food {
        Some(Peeled(food)) => Some(Choped(food)),
        None => None,
    }
}
// 烹饪
fn cook(choped_food: Option<Choped>) -> Option<Cooked> {
    match choped_food {
        Some(Choped(food)) => Some(Cooked(food)),
        None => None,
    }
}
// 吃
fn eat(food: Option<Cooked>) {
    match food {
        Some(Cooked(food)) => println!("俺今天吃了{food}"),
        None => println!("没吃"),
    }
}

let real_food = Some(String::from("猪头肉"));
eat(cook(chop(peel(real_food))));

fn process_food(food: Option<String>) -> Option<Cooked> {
    food.map(|f| Peeled(f))
        .map(|Peeled(f)| Choped(f))
        .map(|Choped(f)| Cooked(f))
}

  let real_food1 = Some(String::from("烧鸡"));
  eat(process_food(real_food1));

enum Food {
    Fish,
    Chiken,
    Cow,
}
// 进行能飞和有腿的检测，能通过的话就用Some包裹起来
fn has_legs(food: Food) -> Option<Food> {
    match food {
        Food::Fish => None,
        _ => Some(food),
    }
}
fn can_fly(food: Food) -> Option<Food> {
    match food {
        Food::Chiken => Some(food),
        _ => None,
    }
}
fn eat1(food: Option<Food>) {
    match food {
        Some(_food) => println!("i can eat it"),
        None => println!("i am hungury"),
    }
}

fn test(food: Food) -> Option<Food> {
    match has_legs(food) {
        None => None,
        Some(food) => match can_fly(food) {
            Some(food) => Some(food),
            None => None,
        },
    }
}

fn test1(food: Food) -> Option<Food> {
    has_legs(food).and_then(can_fly)
}

 eat1(test(Food::Chiken));
 eat1(test(Food::Fish));
 eat1(test1(Food::Cow));