Swiftプロトコルで使用されている一般的なタイプは動作していません

Question

私はGeneric Typeとプロトコルを使用する小さなデモを簡単にしています。

protocol Food { 

} 

class Meat: Food { 

} 

class Cake: Food { 

} 

protocol EatProtocol { 
    func eat<T: Food>(_: T) 
} 

class Person: EatProtocol { 
    func eat<T>(_: T) where T : Food { 
     print("eat food") 
    } 
} 

class Man: Person { 
    override func eat<T>(_: T) where T : Meat { 
     print("eat meat") 
    } 
} 

class Woman: Person { 
    override func eat<T>(_: T) where T : Cake { 
     print("eat cake") 
    } 
} 

let man = Man() 
let woman = Woman() 
let manyPeople: [EatProtocol] = [man, woman] 

let meat = Meat() 
let cake = Cake() 
let manyFood: [Food] = [meat, cake] 

for (index, people) in manyPeople.enumerated() { 
    let food = manyFood[index] 
    people.eat(food)//error: Cannot invoke 'eat' with an argument list of type '(Food)' 
} 

問題は、私は、forループの項目で右食品を得ることを確信しているが、コンパイラがそのエラーに私

Answer 1

を与える根本的な問題がここにあります：すべての食べる人は、食品のすべての種類を食べることができます。私は、この特定の例ではと考えることができる最高の安全にキャスト可能な組み合わせを、列挙、および呼び出しを行うためにswitchを使用することです：

protocol Food {} 
class Meat: Food {} 
class Cake: Food {} 

protocol Eater { 
    func eat<T: Food>(_: T) 
} 

class Person: Eater { 
    func eat<T>(_: T) where T: Food { 
     print("eat food") 
    } 
} 

class Man: Person { 
    override func eat<T>(_: T) where T: Meat { 
     print("eat meat") 
    } 
} 

class Woman: Person { 
    override func eat<T>(_: T) where T : Cake { 
     print("eat cake") 
    } 
} 

let eaters: [Eater] = [Man(), Woman()] 
let foods: [Food] = [Cake(), Cake()] 

for (food, eater) in zip(foods, eaters) { 
    switch (food, eater) { 
     case let (meat as Meat, man as Man): man.eat(meat) 
     case let (cake as Cake, woman as Woman): woman.eat(cake) 
     //... 
     default: 
      print("\(eater) (of type: \(type(of: eater))) cannot eat \(food) (of type: \(type(of: food)))") 
      continue 
    } 
}