Alamofire（六）--|Alamofire（六）-- 响应封装Response Alamofire（六）--响应封装Respo

引言当我们完成Request的时候，肯定要处理服务器返回的响应数据，在之前的文章中，我们讲过Alamofire中，把Request分为了4类Request：

DataRequest

DownloadRequest

UploadRequest

StreamRequest

所以，有4种不同的Request类型，那么就有与之对应的不同的Response。
StreamRequest因为之前没有提过，在这里，我们也不先提，然后UploadRequest，服务器的数据响应其实很简单，只需响应一个结果，因此，是不需要对它的Response再次进行独立的封装了。
所以，我们这里讲到2种与之相对应的Response类型，它们是：

DefaultDataResponse/DataResponse

DefaultDownloadResponse/DownloadResponse

看下代码：

/// Adds a handler to be called once the request has finished. /// /// - parameter queue:The queue on which the completion handler is dispatched. /// - parameter completionHandler: The code to be executed once the request has finished. /// /// - returns: The request. @discardableResult public func response(queue: DispatchQueue? = nil, completionHandler: @escaping (DefaultDataResponse) -> Void) -> Self { delegate.queue.addOperation { (queue ?? DispatchQueue.main).async { var dataResponse = DefaultDataResponse( request: self.request, response: self.response, data: self.delegate.data, error: self.delegate.error, timeline: self.timeline )dataResponse.add(self.delegate.metrics)completionHandler(dataResponse) } }return self }

当我使用这个函数方法获取响应数据，这里获取到的数据是没有经过序列化处理的数据，所以，我们这样区分，如果是返回的带有Default开头的响应者，如DefaultDataResponse、DefaultDownloadResponse，这些都是没有进过序列化处理的response方法。相反的，如果使用了序列化处理过的response方法，返回的，应该就是DataResponse或者是DownloadResponse。
其实，这样的设计，更好的理解一些，我们在实际项目种，也不会把所有的参数都放在一个模型中。
接下来，我们来慢慢讲讲这些响应方法。
DefaultDataResponse 属性 DefaultDataResponse用于响应data或者upload请求的未经过序列化处理的的数据。看看代码：

/// The URL request sent to the server. public let request: URLRequest?/// The server's response to the URL request. public let response: HTTPURLResponse?/// The data returned by the server. public let data: Data?/// The error encountered while executing or validating the request. public let error: Error?/// The timeline of the complete lifecycle of the request. public let timeline: Timelinevar _metrics: AnyObject?

request: URLRequest?：表示该响应来源于那个请求

response: HTTPURLResponse?：服务器返回的响应

data: Data?：响应数据

error: Error?：在请求中可能发生的错误

timeline: Timeline：请求的时间线封装

_metrics: AnyObject?：包含了请求和响应的统计信息

为了保存数据，Alamofire把这个类设计成了struct，对数据操作更安全。
构造函数当然，Alamofire还提供了一个构造函数：

/// Creates a `DefaultDataResponse` instance from the specified parameters. /// /// - Parameters: ///- request:The URL request sent to the server. ///- response: The server's response to the URL request. ///- data:The data returned by the server. ///- error:The error encountered while executing or validating the request. ///- timeline: The timeline of the complete lifecycle of the request. `Timeline()` by default. ///- metrics:The task metrics containing the request / response statistics. `nil` by default. public init( request: URLRequest?, response: HTTPURLResponse?, data: Data?, error: Error?, timeline: Timeline = Timeline(), metrics: AnyObject? = nil) { self.request = request self.response = response self.data = https://www.it610.com/article/data self.error = error self.timeline = timeline }

DataResponse 属性一样的，我们先来看看它有些什么属性：

/// Used to store all data associated with a serialized response of a data or upload request. public struct DataResponse { /// The URL request sent to the server. public let request: URLRequest?/// The server's response to the URL request. public let response: HTTPURLResponse?/// The data returned by the server. public let data: Data?/// The result of response serialization. public let result: Result/// The timeline of the complete lifecycle of the request. public let timeline: Timeline/// Returns the associated value of the result if it is a success, `nil` otherwise. public var value: Value? { return result.value }/// Returns the associated error value if the result if it is a failure, `nil` otherwise. public var error: Error? { return result.error }var _metrics: AnyObject?

对比我们上面的DefaultDataResponse，可以看到，DataResponse多了一个result属性，该属性的存在，即是存储了序列化后的数据。result属性的类型是Result，关于Result的内容，我们后面会单独讲到，这里不在详述。
构造函数同样的，Alamofire也提供了一个构造函数：

/// Creates a `DataResponse` instance with the specified parameters derived from response serialization. /// /// - parameter request:The URL request sent to the server. /// - parameter response: The server's response to the URL request. /// - parameter data:The data returned by the server. /// - parameter result:The result of response serialization. /// - parameter timeline: The timeline of the complete lifecycle of the `Request`. Defaults to `Timeline()`. /// /// - returns: The new `DataResponse` instance. public init( request: URLRequest?, response: HTTPURLResponse?, data: Data?, result: Result, timeline: Timeline = Timeline()) { self.request = request self.response = response self.data = https://www.it610.com/article/data self.result = result self.timeline = timeline }

扩展不仅如此，我们往下可以看到，DataResponse还有扩展属性：

extension DataResponse: CustomStringConvertible, CustomDebugStringConvertible { /// The textual representation used when written to an output stream, which includes whether the result was a /// success or failure. public var description: String { return result.debugDescription }/// The debug textual representation used when written to an output stream, which includes the URL request, the URL /// response, the server data, the response serialization result and the timeline. public var debugDescription: String { var output: [String] = []output.append(request != nil ? "[Request]: \(request!.httpMethod ?? "GET") \(request!)" : "[Request]: nil") output.append(response != nil ? "[Response]: \(response!)" : "[Response]: nil") output.append("[Data]: \(data?.count ?? 0) bytes") output.append("[Result]: \(result.debugDescription)") output.append("[Timeline]: \(timeline.debugDescription)")return output.joined(separator: "\n") } }

DataResponse实现了CustomStringConvertible和CustomDebugStringConvertible协议，因此可以自定义DataResponse的打印信息。
我们也可以给我们模型实现这两个协议，在代码调试的时候，打印出详细的信息，比打断点来查看效率更高。
DefaultDownloadResponse 属性我们来看下它的属性定义：

/// The URL request sent to the server. public let request: URLRequest?/// The server's response to the URL request. public let response: HTTPURLResponse?/// The temporary destination URL of the data returned from the server. public let temporaryURL: URL?/// The final destination URL of the data returned from the server if it was moved. public let destinationURL: URL?/// The resume data generated if the request was cancelled. public let resumeData: Data?/// The error encountered while executing or validating the request. public let error: Error?/// The timeline of the complete lifecycle of the request. public let timeline: Timelinevar _metrics: AnyObject?

有很多属性和前面的都有重复，我们就不说了，来看看不同的。

temporaryURL: URL?：下载成功后，数据会被保存在这个临时URL中

destinationURL: URL?：目标URL，如果设置了该属性，那么文件会复制到该URL中

resumeData: Data?：表示可恢复的数据，对于下载任务，如果因为某种原因下载中断了，或失败了，可以使用该数据恢复之前的下载

构造函数同样，也有相应的构造方法：

/// Creates a `DefaultDownloadResponse` instance from the specified parameters. /// /// - Parameters: ///- request:The URL request sent to the server. ///- response:The server's response to the URL request. ///- temporaryURL:The temporary destination URL of the data returned from the server. ///- destinationURL: The final destination URL of the data returned from the server if it was moved. ///- resumeData:The resume data generated if the request was cancelled. ///- error:The error encountered while executing or validating the request. ///- timeline:The timeline of the complete lifecycle of the request. `Timeline()` by default. ///- metrics:The task metrics containing the request / response statistics. `nil` by default. public init( request: URLRequest?, response: HTTPURLResponse?, temporaryURL: URL?, destinationURL: URL?, resumeData: Data?, error: Error?, timeline: Timeline = Timeline(), metrics: AnyObject? = nil) { self.request = request self.response = response self.temporaryURL = temporaryURL self.destinationURL = destinationURL self.resumeData = https://www.it610.com/article/resumeData self.error = error self.timeline = timeline }

DownloadResponse 其实，也没有什么可以说了，类比上面的内容，比较学习一下，都差不多的意思，这里就不在详细说了。
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