observableObject 没有更新视图

Question

我有两个视图（主视图和过滤器）。 对于我的过滤器视图，用户可以从中选择一些选择器，这些选择器将过滤在数组中硬编码的数据。 在主视图中，数组在 for each 循环中被调用，该循环将在 LazyVGrid 视图上显示数据。 但是，由于某种原因，当我过滤数据时视图没有更新。

过滤器视图

import SwiftUI

struct Filter: View {
@Binding  var sortIndex: Int
@ObservedObject var model: MarketDataViewModel

var sort = ["Best Match", "Newest", "Lowest to Highest", "Highest to Lowest"]

var body: some View {
    Form {
        Section(header: Text("General Settings")){
            
            
            Picker(selection: $sortIndex, label: Text("Sort by")) {
                ForEach(0..<sort.count) {
                    Text(self.sort[$0])
                }
            }.onChange(of: sortIndex, perform: { value in
                model.data.sort(by: {$0.price < $1.price})
                print(model.data)
                print("__________________________________")
            })
        
    } .navigationBarTitle("Filters")
  }
}

主视图

import SwiftUI

结构市场：查看{

@State var text = ""
@State  var sortIndex = 0
@State private var isEditing = false
@StateObject var item = MarketDataViewModel()

var body: some View {
    NavigationView {
        VStack {
            HStack{
                SearchBar(text: $text)
                NavigationLink(destination: Filter(sortIndex: $sortIndex, model: MarketDataViewModel())) {
                    Image("Filter")
                        .resizable()
                        .frame(width: 33, height: 33, alignment: .trailing)
                }
                Spacer()
                    .frame(width: 15)
            }

            ScrollView {
                LazyVGrid(columns: [.init(), .init()]) {
                    ForEach(item.data.filter({"\($0.itemName)".contains(text) || text.isEmpty})) { item in
                        NavigationLink(destination: DescriptionView(item: item), label: {
                            GroupBox(
                                label: Image(item.image)
                                    .resizable()
                                    .scaledToFit()
                                    .frame(width: 100,height: 100)
                                    .cornerRadius(4)
                                    .padding(.vertical, 10)
                                    .padding(.horizontal, 20)
                            ) {
                                VStack(alignment: .center, spacing: 5) {
                                    Text(item.itemName)
                                        .fontWeight(.semibold)
                                        .foregroundColor(Color.black)
                                        .lineLimit(2)
                                        .minimumScaleFactor(0.5)
                                    
                                    Text("$\(item.price, specifier: "%.2f")")
                                        .font(.subheadline)
                                        .foregroundColor(.secondary)
                                }
                            }
                        })
                    }
                }
                .padding()
            }
        }
        .navigationBarHidden(true)
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }
  }

}

数据

struct MarketData : Identifiable {
var id = UUID()
var itemName = String()
var image = String()
var description = String()
var price = Double()
var pfp = String() 
}

class MarketDataViewModel: ObservableObject {

@Published var data: [MarketData] = [MarketData(id: UUID(), itemName: "Boots", image: "Boots", description: "Just a pair of boots", price: 30.00, pfp: "Profile"),
                                     
                                     MarketData(id: UUID(), itemName: "Santa", image: "Santa", description: "Ho Ho Ho. I am santa", price: 100.00, pfp: "Profile"),
                                     
                                     MarketData(id: UUID(), itemName: "Snowflake", image: "Snowflake", description: "Snow", price: 0, pfp: "Profile"), MarketData(id: UUID(), itemName: "Car", image: "Car", description: "The most expensive thing on this entire database right now.", price: 100000000, pfp: "Profile"),
                                     
                                     MarketData(id: UUID(), itemName: "Robo Boots", image: "Robot Boots", description: "Bootleg IronMan", price: 3440.00, pfp: "Profile"),
                                     MarketData(id: UUID(), itemName: "Boots SM", image: "Boots", description: "Just a pair of boots", price: 310.00, pfp: "Profile"),
                                     MarketData(id: UUID(), itemName: "Boots M", image: "Boots", description: "Just a pair of boots", price: 500.00, pfp: "Profile"),
                                     MarketData(id: UUID(), itemName: "Boots XXL", image: "Boots", description: "Just a pair of boots", price: 30.40, pfp: "Profile"),
                                     MarketData(id: UUID(), itemName: "Boots For Sale", image: "Boots", description: "Just a pair of boots", price: 31.00, pfp: "Profile"),
                                     MarketData(id: UUID(), itemName: "Boots Not For Sale", image: "Boots", description: "Just a pair of boots", price: 60.00, pfp: "Profile"),
                                     MarketData(id: UUID(), itemName: "Fake Boots", image: "Boots", description: "Just a pair of boots", price: 10.00, pfp: "Profile")]

}

Answer 1

在这里， NavigationLink(destination: Filter(sortIndex: $sortIndex, model: MarketDataViewModel()))每次单击它时都会创建一个新的MarketDataViewModel 。 你应该有： NavigationLink(destination: Filter(sortIndex: $sortIndex, model: item)) 。 这样你就可以使用单一的事实来源，你的@StateObject var item = MarketDataViewModel() 。