\`==\`与\`hashValue`

Fruit_r01.swift

class Fruit:Hashable {
    let name:String
    
    var hashValue: Int {
        return name.hashValue
    }
    
    init(name:String) {
        self.name = name
    }
    
    static func ==(lhs: Fruit, rhs: Fruit) -> Bool {
        return type(of:lhs) == type(of:rhs) && lhs.name == rhs.name
    }
}

class Apple:Fruit {
    override var hashValue: Int {
        return super.hashValue - "apple".characters.count
    }
}

class Banana:Fruit {
    override var hashValue: Int {
        return super.hashValue - "banana".characters.count
    }
}

let a = Apple(name: "")
let b = Banana(name: "")
print(a == b) // false
print(a.hashValue) // prints 4799450059485596700
print(b.hashValue) // prints 4799450059485596699