Question

我有一个字典数组，需要检查一个键值对是否存在，如果不返回默认值。

使用下面的代码，我可以找到一个键值对（如果存在）。

let arrayOfDicts = [["Name": "JW", "amount": 50], ["Name": "Red Wine", "amount": 50], ["Name": "White Wine", "amount": 50], ["Name": "X", "amount": 50], ["Name": "JW", "amount": 50], ["Name": "Y", "amount": 50], ["Name": "Y", "amount": 50]]

let nameToFind = "Smirnoff"
var amount = ""

for i in 0..<arrayOfDicts.count{
    if arrayOfDicts[i]["ingredient"] as! String == nameToFind {
        amount = arrayOfDicts[i]["usedAmount"] as! String
    }
}

但是如果键对值不存在，我需要返回一个默认值（假设为“ 0”）。

Answer 1

最好

struct Item {
    let name:String
    let amount:Double
}


let arrayOfDicts = [Item(name: "pppp", amount: 23)] 

func getValue(_ name:String) -> Double { 
    return arrayOfDicts.first(where: { $0.name == name })?.amount ?? 0 
}

Answer 2

在filter(_:)上使用 arrayOfDicts 来过滤所有带有"Name" == nameToFind的元素，即

let arrayOfDicts = [["Name": "JW", "amount": 50], ["Name": "Red Wine", "amount": 50], ["Name": "White Wine", "amount": 50], ["Name": "X", "amount": 50], ["Name": "JW", "amount": 50], ["Name": "Y", "amount": 50], ["Name": "Y", "amount": 50]]
let nameToFind = "Smirnoff"
var amount = ""

let filteredDict = arrayOfDicts.filter {
    if let name = $0["Name"] as? String {
        return name == nameToFind
    }
    return false
}

要获取amount，请使用

amount = "\((filteredDict.first?["amount"] as? Int) ?? 0)"

如何检查字典数组中是否存在键值对？

2 个答案: