Protocols/面向协议编程, DependencyInjection/依赖式注入的使用

1. Protocols 定义实现协议，面向协议编码

1.1 创建面向协议实例 ProtocolsBootcamp.swift

import SwiftUI/// 颜色样式协议
protocol ColorThemeProtocol {var primary: Color { get }var secondary: Color { get }var tertiary: Color { get }
}struct DefaultColorTheme: ColorThemeProtocol {let primary: Color   = .bluelet secondary: Color = .whitelet tertiary: Color  = .gray
}struct AlternativeColorTheme: ColorThemeProtocol {let primary: Color   = .redlet secondary: Color = .whitelet tertiary: Color  = .orange
}struct AnotherColorTheme: ColorThemeProtocol{var primary: Color  = .bluevar secondary: Color = .redvar tertiary: Color  = .purple
}/// 定义按钮文字协议
protocol ButtonTextProtocol{var buttonText: String { get }
}protocol ButtonPressedProtocol{func buttonPressed()
}protocol ButtonDataSourceProtocol: ButtonTextProtocol, ButtonPressedProtocol{
}class DefaultDataSource: ButtonDataSourceProtocol{var buttonText: String = "Protocols are awesome!"func buttonPressed(){print("Button was pressed!")}
}class AlternativeDataSource: ButtonTextProtocol{var buttonText: String = "Protocols are lame."
}/// 面向协议
struct ProtocolsBootcamp: View {let colorTheme: ColorThemeProtocollet dataSource: ButtonDataSourceProtocolvar body: some View {ZStack {colorTheme.tertiary.ignoresSafeArea()Text(dataSource.buttonText).font(.headline).foregroundColor(colorTheme.secondary).padding().background(colorTheme.primary).cornerRadius(10).onTapGesture {dataSource.buttonPressed()}}}
}struct ProtocolsBootcamp_Previews: PreviewProvider {static var previews: some View {// DefaultColorTheme / AlternativeColorTheme / AnotherColorThemeProtocolsBootcamp(colorTheme: DefaultColorTheme(), dataSource: DefaultDataSource())}
}

1.2 效果图:

2. DependencyInjection 依赖式注入

2.1 创建依赖式注入的实例 DependencyInjectionBootcamp.swift

import SwiftUI
import Combine// Problems with singletons
// 1. Singleton's are GLOBAL      单例模式是全局的
// 2. Can't customize the init!   不能自定义初始化
// 3. Can't swap out dependencies 不能交换式依赖
struct PostsMode: Identifiable, Codable{let userId: Intlet id: Intlet title: Stringlet body: String
}/// 定义协议 数据服务
protocol DataServiceProtocol {/// 获取数据func getData() -> AnyPublisher<[PostsMode], Error>
}/// 生产者数据服务
class ProductionDataService: DataServiceProtocol{/// 单例 Singleton// static let instance = ProductionDataService()let url: URLinit(url: URL) {self.url = url}func getData() -> AnyPublisher<[PostsMode], Error>{URLSession.shared.dataTaskPublisher(for: url).map({$0.data}).decode(type: [PostsMode].self, decoder: JSONDecoder()).receive(on: DispatchQueue.main).eraseToAnyPublisher()}
}/// 模拟请求服务器返回数据
class MockDataService: DataServiceProtocol{let testData: [PostsMode]init(data: [PostsMode]? ) {self.testData = data ?? [PostsMode(userId: 1, id: 1, title: "One", body: "One"),PostsMode(userId: 2, id: 2, title: "Two", body: "Two"),PostsMode(userId: 3, id: 3, title: "Three", body: "Three")]}func getData() -> AnyPublisher<[PostsMode], Error> {Just(testData).tryMap({ $0 }).eraseToAnyPublisher()}
}/// 依赖试
class Dependencies {let dataService: DataServiceProtocolinit(dataService: DataServiceProtocol) {self.dataService = dataService}
}/// ViewModel
class DependencyInjectionViewModel: ObservableObject{@Published var dataArray: [PostsMode] = []var cancellables =  Set<AnyCancellable>()let dataService: DataServiceProtocolinit(dataService: DataServiceProtocol) {self.dataService = dataServiceloadPosts()}private func loadPosts(){dataService.getData().sink { _ in} receiveValue: {[weak self] returnedPosts inself?.dataArray = returnedPosts}.store(in: &cancellables)}
}/// 依赖注入
struct DependencyInjectionBootcamp: View {@StateObject private var vm: DependencyInjectionViewModelinit(dataService: DataServiceProtocol){_vm = StateObject(wrappedValue: DependencyInjectionViewModel(dataService: dataService))}var body: some View {ScrollView {VStack {ForEach(vm.dataArray) { post inText(post.title)Divider()}}}}
}struct DependencyInjectionBootcamp_Previews: PreviewProvider {// static let dataService = ProductionDataService(url: URL(string: "https://jsonplaceholder.typicode.com/posts")!)static let dataService = MockDataService(data: [PostsMode(userId: 12, id: 12, title: "test", body: "test"),PostsMode(userId: 123, id: 123, title: "123", body: "123")])static var previews: some View {DependencyInjectionBootcamp(dataService: dataService)}
}