问RealmSwift获取每个T对象

EN

protocol Countable {

    var value: Int { get }
    init(value: Int)
}


class User: Countable {

    var value: Int = 0

    required convenience init(value: Int) {
        self.init()
        self.value = value
    }
}


class UserGroup<T: Countable> {

    func calculateTotal() {
        let users: [T] = [T(value: 2), T(value: 21)]
        let total = users.flatMap { ($0 as Countable).value }.reduce(0) { $0 + $1 }
        print("total", total)
    }
}

let userGroup = UserGroup<User>()
userGroup.calculateTotal()