Swift 泛型控制台输出

Posted 2023-02-24

【中文标题】Swift 泛型控制台输出

【英文标题】：Swift Generics Console Output

【发布时间】：2014-09-21 12:14:38

【问题描述】：

在 Playground 中启用此类后，我丢失了在此类上方编写的所有控制台输出。这有什么问题？奇怪的是，它在 switch 语句中显示错误“预期模式”一段时间，然后错误消失了

class Cart<T> 
    var customerName: String
    var customerEmail: String
    var items: [T]
    var itemCount: Int 
        return items.count
    
    var promoCode: String? = nil
    init(customerName: String, customerEmail: String)
        self.customerName = customerName
        self.customerEmail = customerEmail
        items = [T]()
    

    func add (item: T) -> () 
        items.append(item)
    

    func clear () -> () 
        items.removeAll(keepCapacity: false)
    

    func remove (position: Int) -> () 
        items.removeAtIndex(position - 1)
    

    func getPromoCodeDisplay () -> (String) 
        if let x = promoCode 
            return "Your promo code is \(x)"
         else 
            return "You do not have a promo code"
        
    

    func getCartStatus () -> (String) 
        switch itemCount 
        case : 0
        return "You have no items in your cart."
        case : 1...3
        return "You have \(itemCount) items in your cart."
        default :
            return "You are an awesome customer!!"
        
    

【参考方案1】：

您在 case 语句中的冒号 (:) 位置错误。

func getCartStatus () -> (String) 
    switch itemCount 
    case 0 :
    return "You have no items in your cart."
    case 1...3 :
    return "You have \(itemCount) items in your cart."
    default :
        return "You are an awesome customer!!"