ContentView.swift

//
//  ContentView.swift
//  Filter
//
//  Created by Paul Wilkinson on 22/6/2024.
//

import SwiftUI

struct ContentView: View {
    @Environment(Filters.self) var filters:Filters
    @Environment(Items.self) var items: Items
    @State var showFilters=false
        var body: some View {
            NavigationView {
                VStack {
                    if items.filteredItems.isEmpty {
                        Text("No items")
                    } else {
                        ItemListView(items:items.filteredItems)
                    }
                }
                
                .navigationTitle("Fruits and Vegetables")
                .navigationBarItems(trailing:
                                        Button(action: { self.showFilters = true}) {
                    Image(systemName:"line.3.horizontal.decrease")
                })
            }
            .sheet(isPresented: self.$showFilters, onDismiss: {
                self.items.filterItems(filters:self.filters.filters)
            }, content: {
                FilterSettingsView()
            })
            .onAppear {
                self.items.filterItems(filters:self.filters.filters)
            }
        }
}

#Preview {
    @State var filters=Filters.sampleFilters
    @State var items=Items.sampleItems
    return ContentView().environment(filters).environment(items)
}

FilterApp.swift

//
//  FilterApp.swift
//  Filter
//
//  Created by Paul Wilkinson on 22/6/2024.
//

import SwiftUI

@main
struct FilterApp: App {
    @State var filters=Filters.sampleFilters
    @State var items=Items.sampleItems
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(filters)
                .environment(items)
        }
    }
}

FilterViews.swift

//
//  FilterViews.swift
//  Filter
//
//  Created by Paul Wilkinson on 22/6/2024.
//

import SwiftUI

struct FilterSettingsView:View {
    @Environment(Filters.self) var filters:Filters
    var body: some View {
        Form {
            ForEach(FilterType.allCases, id:\.self) { filtertype in
                Section( filtertype.rawValue) {
                    FilterListView(filters:filters.filters(ofType: filtertype))
                }
            }
        }
    }
}

struct FilterListView:View {
    var filters:[Filter]
    var body: some View {
        ForEach(filters) { filter in
            Toggle(isOn: Binding(get: {
                return filter.isOn
            }, set: { isOn in
                filter.isOn = isOn
            })) {
                Text(filter.filterValue)
            }
        }
    }
}

ItemListView.swift

//
//  ItemListView.swift
//  Filter
//
//  Created by Paul Wilkinson on 22/6/2024.
//

import SwiftUI

struct ItemListView: View {
    var items:[Item]
    var body: some View {
        List(items) { item in
            Text(item.name)
        }
    }
}

#Preview {
    ItemListView(items:Items.sampleItems.filteredItems)
}

Models.swift

//
//  Models.swift
//  Filter
//
//  Created by Paul Wilkinson on 22/6/2024.
//

import Foundation
import SwiftUI

enum FilterType: String, CaseIterable {
    case type = "Type"
    case color = "Color"
}

@Observable class Filter: Identifiable {
    init(type:FilterType, filterValue:String, isOn:Bool=false) {
        self.type=type
        self.filterValue=filterValue
        self.isOn=isOn
    }
    
    let id=UUID()
    let type: FilterType
    let filterValue: String
    var isOn: Bool
    
    
}
@Observable class Filters {
    init(filters:[Filter]) {
        self.filters=filters
    }
    var filters=[Filter]()
    func filters(ofType type:FilterType)-> [Filter] {
        return filters.filter({ $0.type == type})
    }
    
    static var sampleFilters = Filters(filters: [Filter(type: .type, filterValue: "Fruit"),Filter(type: .type, filterValue: "Vegetable"),Filter(type: .color, filterValue: "Green"),Filter(type: .color, filterValue: "Red")])
}

struct Item: Identifiable {
    let name: String
    let type: String
    let color: String
    let id = UUID()
}

@Observable class Items {
    var filteredItems:[Item]
    var allItems:[Item]
    init(items:[Item]) {
        self.allItems = items
        self.filteredItems=items
    }
    
    func filterItems(filters:[Filter]) {
        let activeFilters = filters.filter{$0.isOn}
        if activeFilters.isEmpty {
            self.filteredItems = allItems
            return
        }
        self.filteredItems = self.allItems.filter { item in
            var typeFiltered = true
            var colorFiltered = true
            for filter in activeFilters {
                switch filter.type {
                case .type:
                    if item.type == filter.filterValue {
                        typeFiltered = false
                    }
                case .color:
                    if (item.color ==
                        filter.filterValue) {
                        colorFiltered = false
                    }
                }
            }
            return typeFiltered && colorFiltered
           
        }
    }
    
    static var sampleItems=Items(items: [Item(name:"Granny Smith",type: "Fruit", color:"Green"),Item(name:"Macintosh",type: "Fruit", color:"Red"),Item(name:"Red Pepper",type: "Fruit", color:"Red"),Item(name:"Beet",type: "Vegetable", color:"Red"),Item(name:"Broccolli",type: "Vegetable", color:"Green"),Item(name:"Green Pepper",type: "Fruit", color:"Green")])
}