arrays - 像购物 list 一样格式化数组

Question

我有一个格式如下的数组:

[“裤子:15.50”，“裤子:15.50”，“套头衫:12.99”，“鞋子:50.00”]

我想这样格式化:

[“2x 裤子:31.00”，“1x 套头衫:12.99”，“1x 鞋子:50.00”]

我试过用这个格式化:

 var counts: [String:Int] = [:]
 var shoppingList = ["Trousers : 15.50", "Trousers : 15.50", "Jumper : 12.99", "Shoes: 50.00"]
 var formattedShoppingList = [String]()

     for item in shoppingList {
         counts[item] = (counts[item] ?? 0) + 1
     }


     for (key, value) in counts {

         let display:String = String(value) + "x " + key
         formattedShoppingList.append(display)

     }

但是我明白了

[“2x 裤子:15.50”，“1x 套头衫:12.99”，“1x 鞋子:50.00”]

如果我使用字典，则不能有重复项。我该如何处理？

Answer 1

我会制作一个结构来表示商品名称/价格对(以及 future 可能的其他数据，例如库存数量)。

struct Item: Hashable {
    let name: String
    let price: Double

    public var hashValue: Int { return name.hashValue ^ price.hashValue }

    public static func ==(lhs: Item, rhs: Item) -> Bool {
        return lhs.name == rhs.name && rhs.price == rhs.price
    }
}

let shoppingList = [
    Item(name: "Trousers", price: 15.50),
    Item(name: "Trousers", price: 15.50),
    Item(name: "Jumper", price: 12.99),
    Item(name: "Shoes", price: 50),
]

let counts = shoppingList.reduce([Item: Int]()){counts, item in
    var counts = counts
    counts[item] = (counts[item] ?? 0) + 1
    return counts
}

let formattedShoppingList = counts.map{ item, count in "\(count)x \(item.name): £\(item.price)" }

print(formattedShoppingList)

["2x Trousers: £15.5", "1x Shoes: £50.0", "1x Jumper: £12.99"]