Question

由于某种原因，当将Observable对象分配给变量然后更改它时，视图将不会更新。但是如果我直接通过其索引访问它-它将会：

不起作用：

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

有效吗

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

我的猜测是关于引用的，但是我不确定：（

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())

Answer 1

您的猜测是正确的！

人对象是引用类型，人对象是值类型。

在here中，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var people = self.mypeople.people[0]行获得人员时，它只是获得并创建一个新的Person（此对象的地址与self.mypeople.people [0]对象有所不同），因此在这种情况下，您期望更改数组中的数据，更改self.mypeople.people[0] = people后必须设置people.name

HERE有关引用类型和值类型的更多详细信息

使用变量时SwiftUI Observable无法更新

1 个答案: