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

Question

>假设我有一些类似于以下内容的KVC兼容对象：

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 ) {
...
}
}

我创建一个实例，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：( 来访问 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，KVC有没有办法从第二个报告中获得标题？

类似的东西

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

Answer 1

使用Swift 的原生 KVC 即使使用结构也可以，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

这里的澄清是：您不需要将 NSObject 类更改为结构。即使是一堂课也可以工作。 我认为这是一个答案。

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]