iOS на SwiftUI: первый экран

struct Service: Identifiable, Hashable {
    let id: Int
    let title: String
    let summary: String
    var badge: String? = nil // не у каждой услуги есть метка — поэтому Optional
}

extension Service {
    static let samples: [Service] = [
        Service(id: 1, title: "Сайт компании", summary: "Страницы услуг, форма заявки, SEO-основа", badge: "Популярное"),
        Service(id: 2, title: "Мобильное приложение", summary: "Нативное приложение для iPhone"),
        Service(id: 3, title: "CRM-система", summary: "Клиенты, сделки и задачи в одном месте"),
        Service(id: 4, title: "Интеграции", summary: "Связка сайта с 1С, оплатой и мессенджерами"),
        Service(id: 5, title: "Аудит сайта", summary: "Скорость, SEO и доступность", badge: "Новое"),
    ]
}

extension Set {
    /// Убирает элемент, если он есть, иначе добавляет.
    mutating func toggle(_ member: Element) {
        if contains(member) {
            remove(member)
        } else {
            insert(member)
        }
    }
}

/// «В заявке: 1 услуга», «… 3 услуги», «… 5 услуг».
func selectedLabel(count: Int) -> String {
    if count == 0 { return "Выберите услуги" }
    let word: String
    switch (count % 10, count % 100) {
    case (1, let lastTwo) where lastTwo != 11:
        word = "услуга"
    case (2...4, let lastTwo) where !(12...14).contains(lastTwo):
        word = "услуги"
    default:
        word = "услуг"
    }
    return "В заявке: \(count) \(word)"
}

import SwiftUI

struct ServiceRow: View {
    let service: Service
    let isSelected: Bool

    var body: some View {
        HStack(spacing: 16) {
            ZStack {
                Circle()
                    .fill(.tint)
                Text(service.title.prefix(1))
                    .font(.headline)
                    .foregroundStyle(.white)
            }
            .frame(width: 40, height: 40)

            VStack(alignment: .leading, spacing: 4) {
                Text(service.title)
                    .font(.headline)
                Text(service.summary)
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
                if let badge = service.badge {
                    Text(badge)
                        .font(.caption)
                        .foregroundStyle(.tint)
                }
            }

            Spacer()

            Image(systemName: isSelected ? "checkmark.circle.fill" : "circle")
                .foregroundStyle(isSelected ? Color.accentColor : Color.secondary)
                .accessibilityHidden(true)
        }
        .padding(.vertical, 4)
        .contentShape(Rectangle())
        .accessibilityElement(children: .combine)
        .accessibilityAddTraits(isSelected ? .isSelected : [])
    }
}

#Preview {
    List {
        ServiceRow(service: Service.samples[0], isSelected: true)
        ServiceRow(service: Service.samples[1], isSelected: false)
    }
}

import SwiftUI

struct ServicesView: View {
    @State private var selectedIDs: Set<Int> = []

    var body: some View {
        List(Service.samples) { service in
            Button {
                selectedIDs.toggle(service.id)
            } label: {
                ServiceRow(service: service, isSelected: selectedIDs.contains(service.id))
            }
            .buttonStyle(.plain)
        }
        .safeAreaInset(edge: .bottom) {
            Text(selectedLabel(count: selectedIDs.count))
                .font(.headline)
                .padding()
        }
    }
}

import SwiftUI

struct ServiceDetailView: View {
    let service: Service
    @Binding var selectedIDs: Set<Int>

    private var isSelected: Bool { selectedIDs.contains(service.id) }

    var body: some View {
        Form {
            Section {
                Text(service.summary)
                if let badge = service.badge {
                    LabeledContent("Метка", value: badge)
                }
            }
            Section {
                Button(isSelected ? "Убрать из заявки" : "Добавить в заявку") {
                    selectedIDs.toggle(service.id)
                }
            }
        }
        .navigationTitle(service.title)
    }
}

#Preview {
    @Previewable @State var selectedIDs: Set<Int> = [1]
    NavigationStack {
        ServiceDetailView(service: Service.samples[0], selectedIDs: $selectedIDs)
    }
}

import Observation

@Observable
final class ServicesModel {
    var services: [Service] = Service.samples
    var selectedIDs: Set<Int> = []

    var label: String { selectedLabel(count: selectedIDs.count) }

    func isSelected(_ id: Int) -> Bool {
        selectedIDs.contains(id)
    }

    func toggle(_ id: Int) {
        selectedIDs.toggle(id)
    }
}

import SwiftUI

struct ServicesView: View {
    @State private var model = ServicesModel()

    var body: some View {
        NavigationStack {
            List(model.services) { service in
                NavigationLink(value: service) {
                    ServiceRow(service: service, isSelected: model.isSelected(service.id))
                }
            }
            .navigationTitle("Услуги")
            .navigationDestination(for: Service.self) { service in
                ServiceDetailView(service: service, selectedIDs: $model.selectedIDs)
            }
            .safeAreaInset(edge: .bottom) {
                Text(model.label)
                    .font(.headline)
                    .frame(maxWidth: .infinity)
                    .padding()
                    .background(.bar)
            }
        }
    }
}

#Preview {
    ServicesView()
}

import SwiftUI

@main
struct ServicesApp: App {
    var body: some Scene {
        WindowGroup {
            ServicesView()
        }
    }
}

import Observation
import Synchronization
import Testing
@testable import Services

@MainActor
struct ServicesTests {
    @Test(arguments: [
        (0, "Выберите услуги"),
        (1, "В заявке: 1 услуга"),
        (3, "В заявке: 3 услуги"),
        (5, "В заявке: 5 услуг"),
        (11, "В заявке: 11 услуг"),
        (21, "В заявке: 21 услуга"),
    ])
    func labelUsesRussianPlurals(count: Int, expected: String) {
        #expect(selectedLabel(count: count) == expected)
    }

    @Test func setToggle() {
        var ids: Set<Int> = []
        ids.toggle(3)
        #expect(ids == [3])
        ids.toggle(3)
        #expect(ids.isEmpty)
    }

    @Test func toggleAddsAndRemoves() {
        let model = ServicesModel()
        model.toggle(2)
        model.toggle(5)
        #expect(model.selectedIDs == [2, 5])
        #expect(model.label == "В заявке: 2 услуги")
        model.toggle(2)
        #expect(model.selectedIDs == [5])
    }

    @Test func structIsCopiedOnAssignment() {
        var copy = Service.samples[1]
        copy.badge = "Хит"
        #expect(Service.samples[1].badge == nil)
    }

    @Test func viewsAreNotifiedAboutChanges() {
        let model = ServicesModel()
        let changed = Mutex(false)
        withObservationTracking {
            _ = model.label
        } onChange: {
            changed.withLock { $0 = true }
        }
        model.toggle(3)
        #expect(changed.withLock { $0 })
    }
}