2

出于某种原因，当将 Observable 的对象分配给变量然后更改它时 - 视图不会更新。但如果我直接通过它的索引访问它 - 它会：

不会工作：

var people = self.mypeople.people[0]
people.name = 'test'

是否有效：

self.mypeople.people[0].name = 'test'

我的猜测是关于参考，但我不确定:(

示例代码：

//: A UIKit based Playground for presenting user interface

import SwiftUI
import PlaygroundSupport
import Combine

struct Person: Identifiable{
    var id: Int
    var name: String

    init(id: Int, name: String){
        self.id = id
        self.name = name
    }

}

class People: ObservableObject{
    @Published var people: [Person]

    init(){
        self.people = [
            Person(id: 1, name:"Javier"),
            Person(id: 2, name:"Juan"),
            Person(id: 3, name:"Pedro"),
            Person(id: 4, name:"Luis")]
    }

}

struct ContentView: View {
    @ObservedObject var mypeople: People = People()

    var body: some View {
        VStack{
            ForEach(mypeople.people){ person in
                Text("\(person.name)")
            }
            Button(action: {
                var people = self.mypeople.people[0]
                // this howver works:
                // self.mypeople.people[0].name = 'Test'
                people.name="Jaime2"
            }) {
                Text("Change name")
            }
        }
    }
}


PlaygroundPage.current.liveView = UIHostingController(rootView: ContentView())
4

1 回答 1

2

你的猜测是正确的！！

People 对象是引用类型，Person 对象是值类型。

从这里我可以通过以下代码检查对象的类型：

func isReferenceType(toTest: Any) -> Bool {
    return type(of: toTest) is AnyObject
}

isReferenceType(toTest: Person(id: 1, name:"Javier")) //false
isReferenceType(toTest: People()) //true

因此，当您通过这一行获取人员时var people = self.mypeople.people[0]，它只是获取并创建新人员（此对象的地址与 self.mypeople.people[0] 对象不同），因此在这种情况下，您希望更改数组中的数据，您必须self.mypeople.people[0] = people 更改后设置people.name

有关引用类型和值类型的更多详细信息，请单击此处

于 2019-12-09T15:34:29.647 回答