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如何更深入使用Moya

Moya 簡介

Moya是一套基於Alamofire的網路抽象層框架。

個人認為Alamofire是基於URLSession上,如何更方便的呼叫請求,而Moya則是基於Alamofire上,通過抽象 URLs 和 parameter等等,更好的管理API。

Moya

基本模板

Moya在對於API的封裝是基於enum,通過對於列舉不同端點的不同用法,生成請求。

enum GitHub {
    case zen
    case userProfile(String)
}

extension GitHub: TargetType {
    var baseURL: URL { return URL
(string: "https://api.github.com")! } var path: String { switch self { case .zen: return "/zen" case .userProfile(let name): return "/users/\(name)" } } var method: Moya.Method { return .get } var task: Task { return
.requestPlain } var sampleData: Data { switch self { case .zen: return "Half measures are as bad as nothing at all.".data(using: String.Encoding.utf8)! case .userProfile(let name): return "{\"login\": \"\(name)\",\"id\": 100}".data(using: String
.Encoding.utf8)! } } var validationType: ValidationType { return .successAndRedirectCodes } var headers: [String: String]? { return nil } } 複製程式碼

通過列舉繼承TargetType,新增細節實現。

var provider = MoyaProvider<GitHub>()
provider.request(target) { response in
    if case .failure(let error) = response {
        receivedError = error
    }
}
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最後生成根據TargetType生成provider進行請求。

到此就是Moya的基本實現。因為過於基本,不再贅述。

Codable

Codable協議是蘋果提供解析資料的協議,在不使用第三方庫,如ObjectMapper,SwiftyJson的情況下,將伺服器返回的JSON資料轉為model。

下面是一個簡單的Codable示例:

struct Demo: Codable {
    var name: String
    var age: Int
}

func decode() {
    let jsonString =  "{\"name\":\"zhangsan\",\"age\":15}" // 模擬JSON資料
    let decoder = JSONDecoder()
    let data = jsonString.data(using: .utf8)!
    let model = try! decoder.decode(Demo.self,from: data)
    print(model) // Demo(name: "zhangsan",age: 15)
}
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MoyaResponse中已經封裝好了對應的處理

 DemoProvider.provider.request(.zen) { (result) in
    switch result {
    case .success(let response):
        if let model = try? response.map(Demo.self) {
            success(model)
        }
    case .failure(let error):
        break
   }
}
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如果資料是在JSON的好幾個層級中,也可以通過設定keypath獲取:

{
    data: {
        name: "test",age: 15
    }
}

try? response.map(Demo.self,atKeyPath: "data")

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要注意的是這裡函式還有一個引數叫做failsOnEmptyData,預設設定為true,如果返回的資料為空,會判定會解析失敗。

EndPoint

EndPoint是Moya的半個內部資料結構,由所用的TargetType生成,它最終被用來生成網路請求。 每個EndPoint 都儲存了下面的資料:

/// A string representation of the URL for the request.
public let url: String

/// A closure responsible for returning an `EndpointSampleResponse`. (單元測試)
public let sampleResponseClosure: SampleResponseClosure

/// The HTTP method for the request.
public let method: Moya.Method

/// The `Task` for the request.
public let task: Task

/// The HTTP header fields for the request.
public let httpHeaderFields: [String: String]?
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在Provider生成時,可以傳入endpointClosure,自定義TargetType到Endpoint的方式。

預設的實現方式:

final class func defaultEndpointMapping(for target: Target) -> Endpoint {
    return Endpoint(
        url: URL(target: target).absoluteString,sampleResponseClosure: { .networkResponse(200,target.sampleData) },method: target.method,task: target.task,httpHeaderFields: target.headers
    )
}
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在這裡可以重新定義Endpoint的生成方式,比如:

// 將所有生成Endpoint改為get方式請求
let endpointClosure = { (target: MyTarget) -> Endpoint in
    let url = URL(target: target).absoluteString
    return Endpoint(url: url,sampleResponseClosure: {.networkResponse(200,target.sampleData)},method: .get,task: target.task)
}
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或者對已經生成的Endpoint修改:

let endpointClosure = { (target: MyTarget) -> Endpoint in
    let defaultEndpoint = MoyaProvider.defaultEndpointMapping(for: target)
    return defaultEndpoint.adding(newHTTPHeaderFields: ["APP_NAME": "MY_AWESOME_APP"])
}
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注意:如果直接對已經初始化的Endpoint修改,只能修改task以及新增header。

Request

在生成Endpoint之後,會從Endpoint再轉為URLRequst進行使用。

Moya的預設實現:

RequestResultClosure = (Result<URLRequest,MoyaError>) -> Void

final class func defaultRequestMapping(for endpoint: Endpoint,closure: RequestResultClosure) {
    do {
     let urlRequest = try endpoint.urlRequest()
        closure(.success(urlRequest))
    } catch MoyaError.requestMapping(let url) {
        closure(.failure(MoyaError.requestMapping(url)))
    } catch MoyaError.parameterEncoding(let error) {
        closure(.failure(MoyaError.parameterEncoding(error)))
    } catch {
        closure(.failure(MoyaError.underlying(error,nil)))
    }
}


 public func urlRequest() throws -> URLRequest {
        guard let requestURL = Foundation.URL(string: url) else {
            throw MoyaError.requestMapping(url)
        }

        var request = URLRequest(url: requestURL)
        request.httpMethod = method.rawValue
        request.allHTTPHeaderFields = httpHeaderFields

        switch task {
        case .requestPlain,.uploadFile,.uploadMultipart,.downloadDestination:
            return request
        case .requestData(let data):
            request.httpBody = data
            return request
......
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因為內部已經實現如何生成Request,大多情況不需要修改urlRequest,而是重新定義requestClosure,對已經生成好的request進行修改,下面是直接修改request的快取策略,以及錯誤處理:

let requestClosure = { (endpoint: Endpoint,done: MoyaProvider.RequestResultClosure) in
    do {
        var request = try endpoint.urlRequest()
        request.cachePolicy = .reloadIgnoringCacheData
        done(.success(request))
    } catch {
        done(.failure(MoyaError.underlying(error)))
    }

}
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stubClosure

stubClosure實現:

 /// Do not stub.
final class func neverStub(_: Target) -> Moya.StubBehavior {
    return .never
}

/// Return a response immediately.
final class func immediatelyStub(_: Target) -> Moya.StubBehavior {
    return .immediate
}

/// Return a response after a delay.
final class func delayedStub(_ seconds: TimeInterval) -> (Target) -> Moya.StubBehavior {
    return { _ in return .delayed(seconds: seconds) }
}
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Moya的預設實現是neverStub,當使用immediatelyStub或者是delayedStub,請求網路時就不會走真實的資料,而是返回Target中SimpleData的資料,一般用於測試API返回資料的處理。

delayedStub相對於immediatelyStub指定了延遲時長,單位是秒。

callbackQueue

可以指定網路請求返回之後的callback執行緒。預設所有的請求將會被Alamofire放入background執行緒中,callbac將會在主執行緒中呼叫。

Manager

public typealias Manager = Alamofire.SessionManager

final class func defaultAlamofireManager() -> Manager {
    let configuration = URLSessionConfiguration.default
    configuration.httpAdditionalHeaders = Manager.defaultHTTPHeaders

    let manager = Manager(configuration: configuration)
    manager.startRequestsImmediately = false
    return manager
}
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Moya中使用的Manager其實就是Alamofire的Manager。

可以設定Timeout,快取策略等等

let manager: SessionManager = {
    let configuration = defaultURLSessionConfiguration
    configuration.requestCachePolicy = .reloadIgnoringLocalCacheData
    configuration.timeoutIntervalForRequest = 20
    let trustPolicyManager = ServerTrustPolicyManager(policies:
        [
            "www.baidu.com": ServerTrustPolicy.disableEvaluation
        ]
    )
    let manager = SessionManager(configuration: configuration,serverTrustPolicyManager: trustPolicyManager)
    return manager
}()
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Plugins

plugins是遵守了PluginType的外掛,一個provider可以方多個Plugin。

PluginType:

public protocol PluginType {
    /// 在傳送request之前,還有機會對request修改
    func prepare(_ request: URLRequest,target: TargetType) -> URLRequest

    /// 傳送之前呼叫
    func willSend(_ request: RequestType,target: TargetType)

    /// 接受Response之後,在觸發callback之前
    func didReceive(_ result: Result<Moya.Response,MoyaError>,target: TargetType)

    /// 在呼叫Callback之前,還能修改result
    func process(_ result: Result<Moya.Response,target: TargetType) -> Result<Moya.Response,MoyaError>
}

public extension PluginType {
    func prepare(_ request: URLRequest,target: TargetType) -> URLRequest { return request }
    func willSend(_ request: RequestType,target: TargetType) { }
    func didReceive(_ result: Result<Moya.Response,target: TargetType) { }
    func process(_ result: Result<Moya.Response,MoyaError> { return result }
}
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在Plugin中可以做很多事情

  • 記錄網路請求
  • 處理隱藏或者顯示網路activity progress
  • 對request進行更多的處理

比如:

struct TestPlugin: PluginType {
    //  對request進行更多的處理
    func prepare(_ request: URLRequest,target: TargetType) -> URLRequest {
        var request = request
        if target is GitHub {
            request.timeoutInterval = 5
        }
        return request
    }
    
    // 記錄網路請求
    func willSend(_ request: RequestType,target: TargetType) {
        print("start")
        print(request.request?.url ?? "")
    }
    
    // 記錄網路請求
    func didReceive(_ result: Result<Response,target: TargetType) {
        print("end")
        switch result {
        case .success(let response):
            print("end success")
            print(response.request?.url ?? "")
        case .failure(let error):
            print("end failure")
            print(error)
        }
    }
    
    // 對返回的result進行修改
    func process(_ result: Result<Response,target: TargetType) -> Result<Response,MoyaError> {
        if case let .failure(error) = result {
            return .failure(MoyaError.underlying(error,nil))
        }
        return result
    }
}
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Moya也對Logger,activity等提供了預設實現的Plugin,更多細節就不詳細說明了。

trackInflights

原始碼看了半天還是看不明白,希望懂的朋友能告訴我是怎麼用的。

MultiTarget

一般場景下,是一個targetType對應一個Provider

let githubProvider = MoyaProvider<GitHub>(stubClosure: MoyaProvider.immediatelyStub,trackInflights: true)
let demoProvider = MoyaProvider<Demo>(stubClosure: MoyaProvider.immediatelyStub,trackInflights: true)
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但是如果像讓這個Provider更通用,可以寫為:

let commonProvider = MoyaProvider<MultiTarget>()
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呼叫的時候指定TargetType即可:

commonProvider.request(MultiTarget(GitHub.zen)) { result in
    ...
}
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