Question

我试图在Swift中添加一些自定义对象中找到的值。我在Playground中使用以下代码：

//Custom Object
class EntryPack: NSObject{
  var date: String!
  var duration: Double!
  var customValues:[CustomValuePack] = [] //Nested array of objects declared below
}

//Another object to nest in the above
class CustomValuePack: NSObject{
  var name:String!
  var value: Double!
}

//Instantiate nested objects
let cv1 = CustomValuePack()
  cv1.name = "Day"
  cv1.value = 1.2
let cv2 = CustomValuePack()
  cv2.name = "Day"
  cv2.value = 1.3
let cv3 = CustomValuePack()
  cv2.name = "Night"
  cv2.value = 2.2

//Instantiate parent objects
let entry1 = EntryPack()
  entry1.date = "bingo"
  entry1.duration = 1.1

  entry1.customValues = [cv1, cv2]

let entry2 = EntryPack()
  entry2.date = "bingo"
  entry2.duration = 2.2

let entry3 = EntryPack()
  entry3.date = "dang"
  entry3.duration = 3.0

//Throw it all together into an array
var package = [entry1, entry2, entry3]

//Predicate for some filtering
let predicate = NSPredicate(format:"date = %@", "bingo")
let results = (package as NSArray).filteredArrayUsingPredicate(predicate) as! [EntryPack]

//Sum all the parent object durations
let sum = results.reduce(0.0) { $0 + $1.duration }

print(sum) // = 3.3

但现在我想为value为CustomValuePack的每个name添加"Day"。

我无法弄清楚如何对嵌套的对象数组进行类似的缩减。我尝试过类似的东西，但会产生语法错误：

let sum2 = results.reduce(0.0) { $0.customValues + $1.customValues.value } //Error

如何对嵌套的对象数组中的值求和？我最终还想应用NSPredicate来按name = Day进行过滤，但我不是那么远爱好。

Answer 1

鉴于MOVE FUNCTION NUMVAL(WS-VALUE) TO WS-VALUE-INTERNAL定义如下

entries

您可以使用名称==＆＃34; Day＆＃34;提取CustomValues。并使用此代码

对值字段求和

let entries = [entry1, entry2, entry3]

改进

您正在使用Swift，但出于某种原因，您的代码中仍然存在大量Objective-C。

这就是我重构代码的方式

let sum = entries
    .flatMap { $0.customValues }
    .filter { $0.name == "Day" }
    .map { $0.value }
    .reduce(0, combine: +)

请注意，现在struct EntryPack { let date: String let duration: Double let customValues:[CustomValuePack] } struct CustomValuePack { let name:String let value: Double } let cv1 = CustomValuePack(name: "Day", value: 1.2) let cv2 = CustomValuePack(name: "Day", value: 1.3) let cv3 = CustomValuePack(name: "Night", value: 2.2) let entry1 = EntryPack(date: "bingo", duration: 1.1, customValues: [cv1, cv2]) let entry2 = EntryPack(date: "bingo", duration: 2.2, customValues: []) let entry3 = EntryPack(date: "dang", duration: 3.0, customValues: [])和EntryPack是值类型的结构。

在Swift中求和嵌套自定义对象的值

1 个答案:

改进