arrays - 如何过滤数组中特定键的值？

Question

我们有返回数组的 json 值:

  "sentMoney": [
                {
                    "amount": 3840.83,
                    "currency": "MXN",
                    "isMajor": false
                },
                {
                    "amount": 200,
                    "currency": "USD",
                    "isMajor": true
                }
            ]

我想做的是过滤它，这样我就可以获得“金额”键的值。这是我到目前为止所拥有的，但我收到“没有下标成员”错误消息:

 let filteredItem = self.postTransferSuccess?.sentMoney.filter{$0["sentMoney"]}[0]
                    self.emailMessage.amount = filteredItem

感谢任何帮助!

Answer 1

由于您的 sentMoney 是具有 字典数组 的键值，您应该这样做:

 let resultObj =  (dict["sentMoney"] as? [[String:Any]])?.filter({ ($0["amount"] as? Double) == someValue }).first // dict should be the name of your dictionary

请记住，您的数据应该如下所示，因此不要使用花括号:

var dict = ["sentMoney": [
   ["amount": 3840.83,"currency": "MXN", "isMajor": false],
   ["amount": 200.0,"currency": "USD","isMajor": true]
  ]
]

您的第二个选择是将您的字典转换为结构，这将变得更容易迭代。

struct Item {
    let amount:Double
    let currency:String
    let isMajor:Bool


    init?(_ dict:[String:Any]?) { //<-- failable init will return a nil if there an empty key
    guard let _dict = dict,
    let amount = _dict["amount"] as? Double,
    let currency = _dict["currency"] as? String,
    let isMajor = _dict["isMajor"] as? Bool
        else { return nil }

    self.amount = amount
    self.currency = currency
    self.isMajor = isMajor
   }

}

现在当你需要迭代时，你会做: var someValue = 200.0

 if let arr = dict["sentMoney"] as? [[String:Any]] {
        let items = arr.flatMap({ Item($0)}) //<-- will remove any optional item from your list
        let singleItem = items.first { $0.amount == someValue } 
     // or arr.flatMap({ Item($0) }).filter({ $0.amount == someValue}).first
  }

(侧节点)不惜一切代价避免使用 !，使用 if let 或 guard 语句来解包你的可选值。