arrays - 按对象 INT 快速过滤对象数组!属性(property)

Question

这是我的对象。

class TicketsCellModel: NSObject {

    var title: String?
    var text: String?
    var price: String?
    var tintColor: UIColor?
    var quantity: Int?
}

这里是一些随机数据

var ticketCellModels: [TicketsCellModel] = {
    var cellOne = TicketsCellModel()
    cellOne.title = "Standard Entry"
    cellOne.text = "This is aa standard entry ticket, it's not sutiable for special events please see the plus ticket for that."
    cellOne.price = "£8.35"
    cellOne.tintColor = UIColor.white
    cellOne.quantity = 0

    var cellThree = TicketsCellModel()
    cellThree.title = "Standard with re-entry"
    cellThree.text = "This is a standard entry ticket but you can come and go as you please during the night."
    cellThree.price = "£8.99"
    cellThree.tintColor = UIColor.white
    cellThree.quantity = 2

    var cell6 = TicketsCellModel()
    cell6.title = "Plus Entry"
    cell6.text = "This is the plus entry ticket for special events."
    cell6.price = "£9.99"
    cell6.tintColor = UIColor.rgb(red: 192, green: 192, blue: 192)
    cell6.quantity = 0

    var cell9 = TicketsCellModel()
    cell9.title = "VIP Entry"
    cell9.text = "Here is some more text that is to act as a description for this thing you will purchase."
    cell9.price = "£12.99"
    cell9.tintColor = UIColor.rgb(red: 255, green: 215, blue: 0)
    cell9.quantity = 4
    return [cellOne, cellThree, cell6, cell9]
}()

我现在正在尝试生成一个新的 TicketsCellModel 数组，但只有那些数量 > 0 的数组。我能够执行以下操作以过滤那些以标题“S”开头的数组

let filteredTicketCellModels = ticketCellModels.filter( { return ($0.title?.starts(with: "S") )! } )
        for item in filteredTicketCellModels {
            print("qty: \(item.title)")
        }

但如果我将其调整为；

let filteredTicketCellModels = ticketCellModels.filter( { return ($0.quantity? > 0)! } )
for item in filteredTicketCellModels {
    print("qty: \(item.quantity)")
}

我收到“二元运算符‘>’不能应用于‘Int’类型的操作数？”和‘国际’”。我找不到任何关于如何为 int 执行此操作的示例

Answer 1

import UIKit

首先你不需要继承NSObject。此外，如果您不需要引用语义，请改用 struct。

struct TicketsCellModel {
  var title: String?
  var text: String?
  var price: String?
  var tintColor: UIColor?
  var quantity: Int?
}

创建[TicketsCellModel] 并不是真的需要使用闭包。只需直接分配元素即可。由于我们使用的是 struct，因此我们不需要创建单独的 init。

var ticketCellModels = [
  TicketsCellModel(
    title: "Standard Entry",
    text: "This is aa standard entry ticket, it's not sutiable for special events please see the plus ticket for that.",
    price: "£8.35",
    tintColor: UIColor.white,
    quantity: 0
  ),
  TicketsCellModel(
    title: "Standard with re-entry",
    text: "This is a standard entry ticket but you can come and go as you please during the night.",
    price: "£8.99",
    tintColor: UIColor.white,
    quantity: 2
  ),
  TicketsCellModel(
    title: "Plus Entry",
    text: "This is the plus entry ticket for special events.",
    price: "£9.99",
    tintColor: UIColor.white,
    quantity: 0
  ),
  TicketsCellModel(
    title: "VIP Entry",
    text: "Here is some more text that is to act as a description for this thing you will purchase.",
    price: "£12.99",
    tintColor: UIColor.white,
    quantity: 4
  )
]

现在，如果你需要访问一个可选的，你必须先打开它。最安全的方法是使用 if let 构造或使用 nil-coalescing operator .

let filteredTicketCellModels = ticketCellModels.filter { $0.quantity ?? 0 > 0 }

print(filteredTicketCellModels)

在上面的示例中，初始化期间没有未知变量，因此非可选属性可能更适合。这样您就不必打开任何东西。

Leo Dabus补充说，建议所有属性都是常量。这样做的方法是用 let 替换所有 var。如果您需要更改属性，您可以创建一个新对象，从旧对象复制属性并将新值添加到已更改的属性。