有没有办法使用 value(forKeyPath:) 访问 KVC 中的数组元素？

Question

假设我有一些符合 KVC 的 objects 类似于以下内容：

class Person : NSObject {
   var office: Office
   var firstName: String
   var lastName: String
   var reports: [Report]

   init( office: Office, 
         firstName: String,
         lastName: String,
         reports: [Report] ) {

      ...

   }
}

class Office : NSObject {
   var building: String
   var room: Int

   init( building: String, 
         room: Int ) {

      ...

   }

}

class Report : NSObject {
   var title: String
   var contents: String 

   init( title: String, 
         contents: String ) {

      ...

   }
}

然后我创建了一个实例，人

let person = Person(
                office: Office( 
                    building: "Main",
                    room: 2 ),
                firstName: "Bob",
                lastName: "Roberts",
                reports: [
                    Report( title: "Today's weather", contents: "..." ),
                    Report( title: "Traffic", contents: "..." ),
                    Report( title: "Stocks", contents: "..." )
                ] )

我可以使用 person.value(forKeyPath:) 访问 person 的属性和嵌套属性，如下所示：

person.value(forKeyPath: "firstName") // "Bob"
person.value(forKeyPath: "office.room" ) // 2

但是，在 KVC 中有没有办法从第二份报告中提取标题？

类似

person.value(forKeyPath: "reports[1].title" ) // "Traffic"

Answer 1

即使使用结构，Swift 的原生 KVC 也是可能的，不需要 ObjC 运行时

struct Person {
    var office: Office
    var firstName: String
    var lastName: String
    var reports: [Report]
}

struct Office {
    var building: String
    var room: Int
}

struct Report {
    var title: String
    var contents: String
}

let person = Person(office: Office(building: "Main", room: 2 ),
                    firstName: "Bob", lastName: "Roberts",
                    reports: [
                        Report( title: "Today's weather", contents: "..." ),
                        Report( title: "Traffic", contents: "..." ),
                        Report( title: "Stocks", contents: "..." )
    ])


let keyPath = \Person.reports[1].title
let title = person[keyPath: keyPath] // "Traffic"

Answer 2

这里澄清一下：不需要把NSObjectclass改成struct。即使是 class 也可以。我把这算作一个答案。

class Person : NSObject {
    var office: Office!
    @objc var firstName: String!
    var lastName: String!
    @objc var reports: [Report]!

    init( office: Office,
          firstName: String,
          lastName: String,
          reports: [Report] ) {
        super.init()
        self.office = office
        self.firstName = firstName
        self.lastName = lastName
        self.reports = reports
    }
}

class Office : NSObject {
    var building: String!
    var room: Int!

    init( building: String,
          room: Int ) {
        self.building = building
        self.room = room
    }
}

class Report : NSObject {
    var title: String!
    var contents: String!

    init( title: String,
          contents: String ) {
        self.title =  title
        self.contents = contents
    }
}

let person = Person(
    office: Office(
        building: "Main",
        room: 2 ),
    firstName: "Bob",
    lastName: "Roberts",
    reports: [
        Report( title: "Today's weather", contents: "..." ),
        Report( title: "Traffic", contents: "..." ),
        Report( title: "Stocks", contents: "..." )
    ] )


person[keyPath: \Person.reports[1].title]

有没有办法使用 value(forKeyPath:) 访问 KVC 中的数组元素？

Is there a way to access an array element in KVC using value(forKeyPath:)?

swift

kvc