iOS 基于 RxSwift + Moya 搭建易测试的网络请求层

内容概览

Moya
RxSwift
实例讲解
总结

Moya

TargetType

/// The protocol used to define the specifications necessary for a `MoyaProvider`.
public protocol TargetType {/// The target's base `URL`.var baseURL: URL { get }/// The path to be appended to `baseURL` to form the full `URL`.var path: String { get }/// The HTTP method used in the request.var method: Moya.Method { get }/// Provides stub data for use in testing.var sampleData: Data { get }/// The type of HTTP task to be performed.var task: Task { get }/// The type of validation to perform on the request. Default is `.none`.var validationType: ValidationType { get }/// The headers to be used in the request.var headers: [String: String]? { get }
}

在遵循这个协议的类型中提供这些属性，可以很方便地定制API请求的各种参数。
而且，由于是属性，所以非常容易进行测试。

MoyaProvider

/// Request provider class. Requests should be made through this class only.
open class MoyaProvider<Target: TargetType>: MoyaProviderType {/// Closure that defines the endpoints for the provider.public typealias EndpointClosure = (Target) -> Endpoint/// Closure that decides if and what request should be performed.public typealias RequestResultClosure = (Result<URLRequest, MoyaError>) -> Void/// Closure that resolves an `Endpoint` into a `RequestResult`.public typealias RequestClosure = (Endpoint, @escaping RequestResultClosure) -> Void/// Closure that decides if/how a request should be stubbed.public typealias StubClosure = (Target) -> Moya.StubBehavior/// A closure responsible for mapping a `TargetType` to an `EndPoint`.public let endpointClosure: EndpointClosure/// A closure deciding if and what request should be performed.public let requestClosure: RequestClosure/// A closure responsible for determining the stubbing behavior/// of a request for a given `TargetType`.public let stubClosure: StubClosure.../// Initializes a provider.public init(endpointClosure: @escaping EndpointClosure = MoyaProvider.defaultEndpointMapping,requestClosure: @escaping RequestClosure = MoyaProvider.defaultRequestMapping,stubClosure: @escaping StubClosure = MoyaProvider.neverStub,callbackQueue: DispatchQueue? = nil,manager: Manager = MoyaProvider<Target>.defaultAlamofireManager(),plugins: [PluginType] = [],trackInflights: Bool = false) {self.endpointClosure = endpointClosureself.requestClosure = requestClosureself.stubClosure = stubClosureself.manager = managerself.plugins = pluginsself.trackInflights = trackInflightsself.callbackQueue = callbackQueue}...
}

实际的请求由MoyaProvider发起，而实例化一个MoyaProvider需要提供一个泛型参数Target。
所以MoyaProvider需要相应的TargetType，然后才能完成请求。

在进行测试的时候，我们可以使用这些Closure去深度定制MoyaProvider实例以实现我们想要的效果。

RxSwift

基于RxSwift去实现网络请求层的优点：

初次接触 RxSwift 的朋友可以简单了解一下：
Learn & Master ⚔️ the Basics of RxSwift in 10 Minutes

实例讲解

Demo 地址：MoyaWithRxSwiftDemo

实现API，并遵循 TargetType 协议

/// 定义首页模块需要用到的API信息
struct HomeAPI {let baseURL: URLlet endpoint: HomeAPIEndpoint
}/// 多个API请求
enum HomeAPIEndpoint {// 如果需要传递参数，可以使用枚举的关联值，比如：case basicInfo(userID: String)case basicInfo case hobbies
}/// 遵循 TargetType 协议，并定制请求参数
extension HomeAPI: TargetType {var path: String {switch endpoint {case .basicInfo:return "basic_info.json"case .hobbies:return "hobbies.json"}}var method: Moya.Method {// 如果有必要，可以根据 endpoint 来改变return .get}/// 每个请求需要用到的参数var task: Task {// 如果endpoint中的枚举有关联值，可以使用 switch 中的 case let 取出关联值return .requestParameters(parameters: [:], encoding: URLEncoding.queryString)}var headers: [String : String]? { nil }/// 不建议将测试数据放到App所在的Targetvar sampleData: Data { Data() }/// 测试时，如果需要测试状态码，就需要重写这个属性。/// TargetType 协议中的默认实现是返回 .none，也就是不校验 statusCodevar validationType: ValidationType { .successAndRedirectCodes }
}

使用 MoyaProvider 发起请求，并处理回调(采用 Observable 实现)

final class HomeNetworkHelper {private let baseURL: URLprivate let moyaProvider: MoyaProvider<HomeAPI>// moyaProvider 采用依赖注入的方式进行初始化，便于测试init(baseURL: URL,moyaProvider: MoyaProvider<HomeAPI> = MoyaProvider<HomeAPI>()) {self.baseURL = baseURLself.moyaProvider = moyaProvider}func fetchBasicInfo() -> Observable<UserBasicInfo> {return Observable.create { (observer) -> Disposable inlet api = HomeAPI(baseURL: self.baseURL, endpoint: .basicInfo)self.requestAPI(api: api, observer: observer)return Disposables.create()}.observeOn(SerialDispatchQueueScheduler(qos: .default)) // 切换到后台线程}func fetchHobbies() -> Observable<UserHobbies> {return Observable.create { (observer) -> Disposable inlet api = HomeAPI(baseURL: self.baseURL, endpoint: .hobbies)self.requestAPI(api: api, observer: observer)return Disposables.create()}.observeOn(SerialDispatchQueueScheduler(qos: .default))}func requestAPI<T: Decodable>(api: HomeAPI, observer: AnyObserver<T>) {// moyaProvider 发起网络请求self.moyaProvider.request(api) { (response) inswitch response {case .success(let value):do {let result = try value.map(T.self, atKeyPath: nil, using: JSONDecoder(), failsOnEmptyData: false)observer.onNext(result)observer.onCompleted()} catch {observer.onError(error)}case .failure(let error):observer.onError(error)}}}
}

订阅 Observable，处理网络请求回调

class ViewController: UIViewController {...private lazy var networkHelper = HomeNetworkHelper(baseURL: baseURL)private let baseURL = URL(string: "https://raw.githubusercontent.com/FicowShen/MoyaWithRxSwiftDemo/master/MoyaWithRxSwiftDemo/json/")!private let disposeBag = DisposeBag()...func loadFirstRow() {networkHelper.fetchBasicInfo().delay(DispatchTimeInterval.milliseconds(500),scheduler: MainScheduler.instance).observeOn(MainScheduler.instance) // 切换到主线程。如果引入了RxCocoa，可以将Observable转换为Driver.subscribe(onNext: { [unowned self] (model) inself.models.insert(model, at: 0)self.myTableView.reloadData()}, onError: { (error) inlogError(error)}).disposed(by: disposeBag)}}

对网络请求层进行单元测试

import XCTest
import Moya
import RxBlocking
@testable import MoyaWithRxSwiftDemoclass MoyaWithRxSwiftDemoTests: XCTestCase {func testHomeAPI() {guard let url = URL(string: "https://apple.com") else {XCTFail()return}var api = HomeAPI(baseURL: url, endpoint: .basicInfo)XCTAssertEqual(api.path, "basic_info.json")api = HomeAPI(baseURL: url, endpoint: .hobbies)XCTAssertEqual(api.path, "hobbies.json")}/// 测试请求成功的情况func testSuccessfulHomeAPIRequest() {// 从项目中的JSON里读取数据用来模拟请求成功后返回的model数据guard let url = URL(string: "https://apple.com"),let basicInfoData = loadDataInJSONFile(fileName: "basic_info") else {XCTFail()return}// endpointClosure 可以用来修改// 如果 MoyaProvider 的 stubClosure 不为空，则 MoyaProvider 不会发起真的网络请求let provider = MoyaProvider<HomeAPI>(endpointClosure: { self.mockEndpointForAPI(api: $0, response: .networkResponse(200, basicInfoData)) },stubClosure: { _ in .immediate })let apiHelper = HomeNetworkHelper(baseURL: url, moyaProvider: provider)// RxBlocking 提供了便捷的方法，可以阻塞住当前线程，然后收集 Observable 中的事件guard let basicInfo = try? apiHelper.fetchBasicInfo().toBlocking().first() else {XCTFail()return}XCTAssertEqual(basicInfo.name, "John")XCTAssertEqual(basicInfo.age, 10)}/// 测试发生网络故障(请求超时等情况)的情况func testNetworkErrorForHomeAPIRequest() {guard let url = URL(string: "https://apple.com") else {XCTFail()return}let expectedError = NSError(domain: "expectedError", code: -1, userInfo: nil)let provider = MoyaProvider<HomeAPI>(endpointClosure: { self.mockEndpointForAPI(api: $0, response: .networkError(expectedError)) },stubClosure: { _ in .immediate })let apiHelper = HomeNetworkHelper(baseURL: url, moyaProvider: provider)expectError(expectedError) {_ = try apiHelper.fetchBasicInfo().toBlocking().first()}}/// 测试请求成功后，响应为错误的情况func testResponseErrorForHomeAPIRequest() {guard let url = URL(string: "https://apple.com") else {XCTFail()return}let expectedError = NSError(domain: "", code: 404, userInfo: nil)let provider = MoyaProvider<HomeAPI>(endpointClosure: {self.mockEndpointForAPI(api: $0, response: .networkResponse(404, Data())) },stubClosure: { _ in .immediate })let apiHelper = HomeNetworkHelper(baseURL: url, moyaProvider: provider)expectError(expectedError) {_ = try apiHelper.fetchBasicInfo().toBlocking().first()}}func mockEndpointForAPI(api: TargetType, response: EndpointSampleResponse) -> Endpoint {return Endpoint(url: api.baseURL.absoluteString,sampleResponseClosure: { response },method: api.method,task: api.task,httpHeaderFields: api.headers)}func loadDataInJSONFile(fileName: String) -> Data? {let bundle = Bundle(for: type(of: self))guard let filePath = bundle.path(forResource: fileName, ofType: "json"),let data = try? Data(contentsOf: URL(fileURLWithPath: filePath)) else {return nil}return data}func expectError(_ expectedError: NSError, inFailedRequest requestOperation: (() throws -> ())) {do {try requestOperation()XCTFail()} catch let error as Moya.MoyaError {switch error {case let .underlying(error as NSError, response):if let response = response {XCTAssertEqual(expectedError.code, response.statusCode)} else {XCTAssertEqual(error.code, expectedError.code)}default:XCTFail()}} catch {XCTFail()}}}

总结

基于 RxSwift + Moya 搭建的网络请求层，具有以下优势：

可以模块化，易于扩展
职责分明，易于测试
函数式编程，操作简洁、顺畅
线程切换，简洁、高效

劣势：

RxSwift 学习成本略高
Moya 基于 Alamofire，需要引入一个网络请求库

参考文章：
Moya Tutorial for iOS: Getting Started
Getting Started With RxSwift and RxCocoa
RxSwift + MVVM: how to feed ViewModels
Testing Your RxSwift Code

转载请注明出处，谢谢~

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