Moya

• 什么是moya，moya是什么？

答：高度抽象的API，默认桥接Alamofire

Moya主要优点：

• 编译时检查API endpoint权限

• 让你使用枚举定义各种不同Target, endpoints

• 把stubs当做一等公民对待，因此测试超级简单。

TargetType

public protocol TargetType {
    var baseURL: NSURL { get }
    var path: String { get }
    var method: Moya.Method { get }
    var parameters: [String: AnyObject]? { get }
    var sampleData: NSData { get }
}

AccountAPI模块，模块实现注册登录的功能

enum AccountAPI {
    case Login(userName: String, passwd: String)
    case Register(userName: String, passwd: String)
}
extension AccountAPI: TargetType {

    var baseURL: NSURL {
        return NSURL(string: "https://www.myapp.com")!
    }
    var path: String {
        switch self {
        case .Login:
            return "/login"
        case .Register:
            return "/register"
        }
    }
    var method: Moya.Method {
        return .GET
    }
    var parameters: [String: AnyObject]? {
        switch self {
        case .Login:
            return nil
        case .Register(let userName, let passwd):
            return ["username": userName, "password": passwd]
        }
    }
    var sampleData: NSData {
        switch self {
        case .Login:
            return "{'code': '666',Token':'55555'}".dataUsingEncoding(NSUTF8StringEncoding)!
        case .Register(let userName, let passwd):
            return "找不到数据"
        }
    }
}

• Providers

let provider = MoyaProvider<AccountAPI>()
provider.request(.Login) { result in
    // `result` is either .Success(response) or .Failure(error)
}

Provider真正做的事情可以用一个流来表示：Target -> Endpoint -> Request 。在这个例子中，它将AccountAPI转换成Endpoint, 再将其转换成为NSRURLRequest。最后将这个NSRURLRequest交给Alamofire去进行网络请求。

• Provider的构造函数

//Moya.swift
public init(endpointClosure: EndpointClosure = MoyaProvider.DefaultEndpointMapping,
        requestClosure: RequestClosure = MoyaProvider.DefaultRequestMapping,
        stubClosure: StubClosure = MoyaProvider.NeverStub,
        manager: Manager = MoyaProvider<Target>.DefaultAlamofireManager(),
        plugins: [PluginType] = []) 

• 3个Closure：

  • endpointClosure、requestClosure、stubClosure。这3个Closure是让我们定制请求,修改请求方式和进行测试时可以用到

• Manager

  • Manager是真正用来网络请求的类，Moya自己并不提供Manager类，Moya只是对其他网络请求类进行了简单的桥接。这么做是为了让调用方可以轻易地定制、更换网络请求的库。比如你不想用Alamofire，可以十分简单的换成其他库

• PluginType

  • PluginType是一个数组 Moya提供了一个插件机制，使我们可以建立自己的插件类来做一些额外的事情。比如写Log，显示“菊花”等。抽离出Plugin层的目的，就是让Provider职责单一，满足开闭原则。把和自己网络无关的行为抽离

EndpointClosure

//Moya.swift
public typealias EndpointClosure = Target -> Endpoint<Target>

• EndpointClosure这个闭包，输入是一个Target，返回Endpoint。

  • Endpoint 是Moya最终进行网络请求前的一种数据结构，它保存了这些数据：

* URL
* HTTP请求方式 (GET, POST, etc).
* 本次请求的参数
* 参数的编码方式 (URL, JSON, custom, etc).
* stub数据的 response(测试用的)

//Endpoint.swift
public class Endpoint<Target> {
    public typealias SampleResponseClosure = () -> EndpointSampleResponse
    public let URL: String
    public let method: Moya.Method
    public let sampleResponseClosure: SampleResponseClosure
    public let parameters: [String: AnyObject]?
    public let parameterEncoding: Moya.ParameterEncoding
      ...
  }

• Moya提供一个DefaultEndpointMapping的函数，来实现这个Target到Endpoint的转换：

//Moya.swift
public final class func DefaultEndpointMapping(target: Target) -> Endpoint<Target> {
     let url = target.baseURL.URLByAppendingPathComponent(target.path).absoluteString
     return Endpoint(URL: url, sampleResponseClosure: {.NetworkResponse(200, target.sampleData)}, method: target.method, parameters: target.parameters)
 }


// 上面的代码只是单纯地创建并返回一个Endpoint实例。然而在很多时候，我们需要自定义这个闭包来做更多额外的事情。后面在stub小节，你会看到，我们用stub模拟API请求失败的场景，给客户端返回一个非200的状态码。为了实现这个功能，在这个闭包里处理相关的逻辑，再合适不过了！或者说这个闭包就是让我们根据业务需求定制网络请求的。

• RequestClosure

//Moya.swift
public typealias RequestClosure = (Endpoint<Target>, NSURLRequest -> Void) -> Void

// RequestClosure这个闭包就是实现将Endpoint -> NSURLRequest，Moya也提供了一个默认实现：

//Moya.swift
public final class func DefaultRequestMapping(endpoint: Endpoint<Target>, closure: NSURLRequest -> Void) {
      return closure(endpoint.urlRequest)
}

// 默认实现也只是简单地调用endpoint.urlRequest取得一个NSURLRequest实例。然后调用了closure。然而，你可以在这里修改这个请求Request, 事实上这也是Moya给你的最后的机会。举个例子, 你想禁用所有的cookie，并且设置超时时间等。那么你可以实现这样的闭包：

let requestClosure = { (endpoint: Endpoint<GitHub>, done: NSURLRequest -> Void) in
    //可以在这里修改request
    let request: NSMutableURLRequest = endpoint.urlRequest.mutableCopy() as NSMutableURLRequest
    request.HTTPShouldHandleCookies = false
    request.timeoutInterval = 20 
    done(request)
}
provider = MoyaProvider(requestClosure: requestClosure)

// 从上面可以清晰地看出，EndpointClosure 和 RequestClosure 实现了 Target -> Endpoint -> NSRequest的转换流

• StubClosure

//Moya.swift
public typealias StubClosure = Target -> Moya.StubBehavior

// StubClosure这个闭包比较简单，返回一个StubBehavior的枚举值。它就是让你告诉Moya你是否使用Stub返回数据或者怎样使用Stub返回数据

//Moya.swift
public enum StubBehavior {
    case Never          //不使用Stub返回数据
    case Immediate      //立即使用Stub返回数据
    case Delayed(seconds: NSTimeInterval) //一段时间间隔后使用Stub返回的数据
}

// Never表明不使用Stub来返回模拟的网络数据
// Immediate表示马上返回Stub的数据
// Delayed是在几秒后返回

Moya默认是不使用Stub来测试

Moya 使用示例

extension AccountAPI: TargetType {
    ...
    var sampleData: NSData {
        switch self {
        case .Login:
            return "{'code': 1,6'Token':'123455'}".dataUsingEncoding(NSUTF8StringEncoding)!
        case .Register(let userName, let passwd):
            return "找不到数据"
        }
    }
}
let endPointAction = { (target: TargetType) -> Endpoint<AccountAPI> in
    let url = target.baseURL.URLByAppendingPathComponent(target.path).absoluteString
    switch target {
    case .Login:
        return Endpoint(URL: url, sampleResponseClosure: {.NetworkResponse(200, target.sampleData)}, method: target.method, parameters: target.parameters)
    case .Register:
        return Endpoint(URL: url, sampleResponseClosure: {.NetworkResponse(404, target.sampleData)}, method: target.method, parameters: target.parameters)
    }
}
let stubAction: (type: AccountAPI) -> Moya.StubBehavior  = { type in
    switch type {
    case .Login:
        return Moya.StubBehavior.Immediate
    case .Register:
        return Moya.StubBehavior.Delayed(seconds: 3)
    }
}
let loginAPIProvider = MoyaProvider<AccountAPI>(
    endpointClosure: endPointAction,
    stubClosure: stubAction
)
self.netProvider = loginAPIProvider

loginAPIProvider.request(AccountAPI.Login(userName: "user", passwd: "123456")) { (result) in
    switch result {
    case .Success(let respones) :
        print(respones)
    case .Failure(_) :
        print("We got an error")
    }
    print(result)
}

// 注意：Moya中Provider对象在销毁的时候会去Cancel网络请求。为了得到正确的结果，你必须保证在网络请求的时候你的Provider不会被释放。否者你会得到下面的错误 “But don’t forget to keep a reference for it in property. If it gets deallocated you’ll see -999 “cancelled” error on response” 。通常为了避免这种情况，你可以将Provider实例设置为类成员变量，或者shared实例

• stub 直接上源码

  • self.sendRequest 发送请求

  • self.stubRequest stub请求

//Moya.swift
public func request(target: Target, queue:dispatch_queue_t?, completion: Moya.Completion) -> Cancellable {
        let endpoint = self.endpoint(target)
        let stubBehavior = self.stubClosure(target)
        var cancellableToken = CancellableWrapper()
        let performNetworking = { (request: NSURLRequest) in
            if cancellableToken.isCancelled { return }
            switch stubBehavior {
            case .Never:
                cancellableToken.innerCancellable = self.sendRequest(target, request: request, queue: queue, completion: completion)
            default:
                cancellableToken.innerCancellable = self.stubRequest(target, request: request, completion: completion, endpoint: endpoint, stubBehavior: stubBehavior)
            }
        }
        requestClosure(endpoint, performNetworking)
        return cancellableToken
    }




//Moya.swift 
internal func stubRequest(target: Target, request: NSURLRequest, completion: Moya.Completion, endpoint: Endpoint<Target>, stubBehavior: Moya.StubBehavior) -> CancellableToken {
        ...
        let stub: () -> () = createStubFunction(cancellableToken, forTarget: target, withCompletion: completion, endpoint: endpoint, plugins: plugins)
        switch stubBehavior {
        case .Immediate:
            stub()
        case .Delayed(let delay):
            let killTimeOffset = Int64(CDouble(delay) * CDouble(NSEC_PER_SEC))
            let killTime = dispatch_time(DISPATCH_TIME_NOW, killTimeOffset)
            dispatch_after(killTime, dispatch_get_main_queue()) {
                stub()
            }
        case .Never:
            fatalError("Method called to stub request when stubbing is disabled.")
        }
        ...
}

• Manager

// Moya并不是一个网络请求的三方库，它只是一个抽象的网络层。它对其他网络库的进行了桥接，真正进行网络请求是别人的网络库（比如默认的Alamofire.Manager）为了达到这个目的Moya做了几件事情：

首先抽象了一个RequestType协议，利用这个协议将Alamofire隐藏了起来，让Provider类依赖于这个协议，而不是具体细节。


//Plugin.swift
public protocol RequestType {
    var request: NSURLRequest? { get }
    func authenticate(user user: String, password: String, persistence: NSURLCredentialPersistence) -> Self
    func authenticate(usingCredential credential: NSURLCredential) -> Self
}


Moya+Alamofire.swift
public typealias Manager = Alamofire.Manager
/// Choice of parameter encoding.
public typealias ParameterEncoding = Alamofire.ParameterEncoding
//让Alamofire.Manager也实现 RequestType协议
extension Request: RequestType { }

// 上面几步，就完成了Alamofire的封装、桥接。正因为桥接封装了Alamofire, 因此Moya的request,最终一定会调用Alamofire的request。简单的跟踪下Moya的Request方法就可以发现sendRequest调用了Alamofire。


//Moya.swift
func sendRequest(target: Target, request: NSURLRequest, queue: dispatch_queue_t?, completion: Moya.Completion) -> CancellableToken {
    //调用Alamofire发起网络请求
    let alamoRequest = manager.request(request)
        ...
}

// 如果你想自定义你自己的Manager, 你可以传入你自己的Manager到Privoder。之后所有的请求都会经过你的这个Manager

let policies: [String: ServerTrustPolicy] = [
    "example.com": .PinPublicKeys(
        publicKeys: ServerTrustPolicy.publicKeysInBundle(),
        validateCertificateChain: true,
        validateHost: true
    )
]
let manager = Manager(
    configuration: NSURLSessionConfiguration.defaultSessionConfiguration(),
    serverTrustPolicyManager: ServerTrustPolicyManager(policies: policies)
)
let provider = MoyaProvider<MyTarget>(manager: manager)

• Plugin

Moya提供还提供插件机制，你可以自定义各种插件，所有插件必须满足PluginType协议

//Plugin.swift
public protocol PluginType {
    /// Called immediately before a request is sent over the network (or stubbed).
    func willSendRequest(request: RequestType, target: TargetType)
    // Called after a response has been received, but before the MoyaProvider has invoked its completion handler.
    func didReceiveResponse(result: Result<Moya.Response, Moya.Error>, target: TargetType)
}

// 协议里只有两个方法，willSendRequest和didReceiveResponse。在进行网络请求之前和收到请求后，Moya会遍历所有的插件。分别去调用插件各自的willSendRequest和didReceiveResponse方法。

// 个人觉得这个插件更像是一个网络回调的Delegate，只是取了一个高大上的名字而已。不过将网络回调抽取出来确实能更好地将无关业务隔离，让Privoder更加专心的做自己的事情。而且以后也非常好扩展。

/*
Moya默认提供了三个插件：
Authentication插件 (CredentialsPlugin.swift)。 HTTP认证的插件。
Logging插件(NetworkLoggerPlugin.swift)。在调试是，输入网络请求的调试信息到控制台
Network Activity Indicator插件（NetworkActivityPlugin.swift）。可以用这个插件来显示网络菊花 /

Network Activity Indicator插件用法示例，在网络进行请求开始请求时添加一个Spinner, 请求结束隐藏Spinner。这里用的是SwiftSpinner

let spinerPlugin = NetworkActivityPlugin { state in
    if state == .Began {
        SwiftSpinner.show("Connecting...")
    } else {
        SwiftSpinner.show("request finish...")
        SwiftSpinner.hide()
    }
let loginAPIProvider = MoyaProvider<AccountAPI>(
    plugins: [spinerPlugin]
)
loginAPIProvider.request(.Login) { _ in }

插件实现代码

插件的源码实现也超级简单。在进行网络请求之前和收到请求后，遍历所有的插件，调用其相关的接口。只是要分别处理下Stub和真正进行网络请求的两种情况

//Moya.swift
func sendRequest(target: Target, request: NSURLRequest, queue: dispatch_queue_t?, completion: Moya.Completion) -> CancellableToken {
        let alamoRequest = manager.request(request)
        let plugins = self.plugins
        // 遍历插件，通知开始请求
        plugins.forEach { $0.willSendRequest(alamoRequest, target: target) }
        // Perform the actual request
        alamoRequest.response(queue: queue) { (_, response: NSHTTPURLResponse?, data: NSData?, error: NSError?) -> () in
            let result = convertResponseToResult(response, data: data, error: error)
            // 遍历插件，通知收到请求
            plugins.forEach { $0.didReceiveResponse(result, target: target) }
            completion(result: result)
        }
        alamoRequest.resume()
        return CancellableToken(request: alamoRequest)
    }
//在测试时，Stub分支的也要，遍历调用一次插件
internal final func createStubFunction(token: CancellableToken, forTarget target: Target, withCompletion completion: Moya.Completion, endpoint: Endpoint<Target>, plugins: [PluginType]) -> (() -> ()) {
        return {
            if (token.canceled) {
                let error = Moya.Error.Underlying(NSError(domain: NSURLErrorDomain, code: NSURLErrorCancelled, userInfo: nil))
                //调用插件
                plugins.forEach { $0.didReceiveResponse(.Failure(error), target: target) }
                completion(result: .Failure(error))
                return
            }
            switch endpoint.sampleResponseClosure() {
            case .NetworkResponse(let statusCode, let data):
                let response = Moya.Response(statusCode: statusCode, data: data, response: nil)
                //成功情况，调用插件
                plugins.forEach { $0.didReceiveResponse(.Success(response), target: target) }
                completion(result: .Success(response))
            case .NetworkError(let error):
                let error = Moya.Error.Underlying(error)
                //失败情况，调用插件
                plugins.forEach { $0.didReceiveResponse(.Failure(error), target: target) }
                completion(result: .Failure(error))
            }
        }
    }

枚举无法重载，代码未必简洁
比如，现在要添加一个新接口，还是要求实现Login功能，除了支持已有的用户名/密码登录，还要支持指纹登录。那么我们想定义可能想这样：Login(fingerPrint: String)。这两种登录情况实际上只是参数不一样。但在因为枚举中不能重载，所以为了添加这个case，我们不得不重新取一个名字，而不能利用函数重载。

enum AccountAPI {
case Login(userName: String, passwd: String)
case Register(userName: String, passwd: String)
//case Login(fingerPrint: String) //error: 不能这样添加错的，不支持重载
case LoginWithPrint(fingerPrint: String) //正确. 只能改名
}

666 哈哈哈哈哈哈哈