一、請求網絡數據

① 通過 rx.response 請求數據

• 如下所示，通過豆瓣提供的音樂頻道列表接口獲取數據，并將返回結果輸出到控制臺中：

"https://www.douban.com/j/app/radio/channels" -i -v Success (2134ms): Status 200 返回的數據是： {"channels":[{"name_en":"Personal Radio","seq_id":0,"abbr_en":"My","name":"私人兆赫","channel_id":0},{"name":"華語","seq_id":0,"abbr_en":"","channel_id":"1","name_en":""},{"name":"歐美","seq_id":1,"abbr_en":"","channel_id":"2","name_en":""},{"name":"七零","seq_id":2,"abbr_en":"","channel_id":"3","name_en":""},{"name":"八零","seq_id":3,"abbr_en":"","channel_id":"4","name_en":""},{"name":"九零","seq_id":4,"abbr_en":"","channel_id":"5","name_en":""},{"name":"粵語","seq_id":5,"abbr_en":"","channel_id":"6","name_en":""},{"name":"搖滾","seq_id":6,"abbr_en":"","channel_id":"7","name_en":""},{"name":"民謠","seq_id":7,"abbr_en":"","channel_id":"8","name_en":""},{"name":"輕音樂","seq_id":8,"abbr_en":"","channel_id":"9","name_en":""},{"name":"原聲","seq_id":9,"abbr_en":"","channel_id":"10","name_en":""},{"name":"Fly by midnight ","seq_id":10,"abbr_en":"","channel_id":"267","name_en":""},{"name":"獨立","seq_id":11,"abbr_en":"","channel_id":"268","name_en":""},{"name":"爵士","seq_id":12,"abbr_en":"","channel_id":"13","name_en":""},{"name":"電子","seq_id":13,"abbr_en":"","channel_id":"14","name_en":""},{"name":"說唱","seq_id":14,"abbr_en":"","channel_id":"15","name_en":""},{"name":"R&B ","seq_id":15,"abbr_en":"","channel_id":"16","name_en":""},{"name":"日語","seq_id":16,"abbr_en":"","channel_id":"17","name_en":""},{"name":"韓語","seq_id":17,"abbr_en":"","channel_id":"18","name_en":""},{"name":"我的巴比倫戀人","seq_id":18,"abbr_en":"","channel_id":"259","name_en":""},{"name":"女聲","seq_id":19,"abbr_en":"","channel_id":"20","name_en":""},{"name":"法語","seq_id":20,"abbr_en":"","channel_id":"22","name_en":""},{"name":"戶外","seq_id":21,"abbr_en":"","channel_id":"151","name_en":""},{"name":"休息","seq_id":22,"abbr_en":"","channel_id":"152","name_en":""},{"name":"工作學習","seq_id":23,"abbr_en":"","channel_id":"153","name_en":""},{"name":"亢奮","seq_id":24,"abbr_en":"","channel_id":"154","name_en":""},{"name":"古典","seq_id":25,"abbr_en":"","channel_id":"27","name_en":""},{"name":"動漫","seq_id":26,"abbr_en":"","channel_id":"28","name_en":""},{"name":"咖啡館","seq_id":27,"abbr_en":"","channel_id":"32","name_en":""},{"name":"舒緩","seq_id":28,"abbr_en":"","channel_id":"155","name_en":""},{"name":"18歲青春的召喚","seq_id":29,"abbr_en":"","channel_id":"262","name_en":""},{"name":"紅歌","seq_id":30,"abbr_en":"","channel_id":"41","name_en":""},{"name":"圣誕","seq_id":31,"abbr_en":"","channel_id":"170","name_en":""},{"name":"運動","seq_id":32,"abbr_en":"","channel_id":"257","name_en":""},{"name":"英語","seq_id":33,"abbr_en":"","channel_id":"264","name_en":""},{"name":"豆瓣好歌曲","seq_id":34,"abbr_en":"","channel_id":"179","name_en":""},{"name":"Future Pop","seq_id":35,"abbr_en":"","channel_id":"266","name_en":""},{"name":"金屬","seq_id":36,"abbr_en":"","channel_id":"187","name_en":""},{"name":"布魯斯","seq_id":37,"abbr_en":"","channel_id":"188","name_en":""},{"name":"新歌","seq_id":38,"abbr_en":"","channel_id":"61","name_en":""},{"name":"世界杯","seq_id":39,"abbr_en":"","channel_id":"201","name_en":""},{"name":"朋克","seq_id":40,"abbr_en":"","channel_id":"76","name_en":""},{"name":"Easy ","seq_id":41,"abbr_en":"","channel_id":"77","name_en":""},{"name":"91.1 ","seq_id":42,"abbr_en":"","channel_id":"78","name_en":""},{"name":"鄉村","seq_id":43,"abbr_en":"","channel_id":"269","name_en":""},{"name":"“磚”屬音樂","seq_id":44,"abbr_en":"","channel_id":"145","name_en":""},{"name":"Pop","seq_id":45,"abbr_en":"","channel_id":"194","name_en":""},{"name":"拉丁","seq_id":46,"abbr_en":"","channel_id":"189","name_en":""}]}

• 請求示例如下：

// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.response(request: request).subscribe(onNext: {(response, data) in// 數據處理let str = String(data: data, encoding: String.Encoding.utf8)print("返回的數據是：", str ?? "") }).disposed(by: disposeBag)

• 從以上示例，可以看到，不管請求成功與否都會進入到 onNext 這個回調中，如果需要根據響應狀態進行一些相應操作，比如：
• • 狀態碼在 200 ~ 300 則正常顯示數據；
• • 如果是異常狀態碼（比如：404）則彈出告警提示框。
• 可以借助 response 參數進行判斷即可，把 url 改成一個錯誤的地址：

// 創建URL對象 let urlString = "https://www.douban.com/xxxxxxxxxx/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.response(request: request).subscribe(onNext: {(response, data) in// 判斷響應結果狀態碼if 200 ..< 300 ~= response.statusCode {let str = String(data: data, encoding: String.Encoding.utf8)print("請求成功！返回的數據是：", str ?? "")}else{print("請求失敗！")} }).disposed(by: disposeBag)

• 運行結果如下：

curl -X GET "https://www.douban.com/xxxxxxxxxx/app/radio/channels" -i -v Failure (1448ms): Status 404 請求失敗！

② 通過 rx.data 請求數據

• rx.data 與 rx.response 的區別：
• • 如果不需要獲取底層的 response，只需知道請求是否成功，以及成功時返回的結果，那么建議使用 rx.data。
• • 因為 rx.data 會自動對響應狀態碼進行判斷，只有成功的響應（狀態碼為 200~300）才會進入到 onNext 這個回調，否則進入 onError 這個回調。
• 如果不需要考慮請求失敗的情況，只對成功返回的結果做處理可以在 onNext 回調中進行相關操作：

// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.data(request: request).subscribe(onNext: {data inlet str = String(data: data, encoding: String.Encoding.utf8)print("請求成功！返回的數據是：", str ?? "") }).disposed(by: disposeBag)

• 運行結果：

"https://www.douban.com/j/app/radio/channels" -i -v Success (1449ms): Status 200 請求成功！返回的數據是： {"channels":[{"name_en":"Personal Radio","seq_id":0,"abbr_en":"My","name":"私人兆赫","channel_id":0},{"name":"華語","seq_id":0,"abbr_en":"","channel_id":"1","name_en":""},{"name":"歐美","seq_id":1,"abbr_en":"","channel_id":"2","name_en":""},{"name":"七零","seq_id":2,"abbr_en":"","channel_id":"3","name_en":""},{"name":"八零","seq_id":3,"abbr_en":"","channel_id":"4","name_en":""},{"name":"九零","seq_id":4,"abbr_en":"","channel_id":"5","name_en":""},{"name":"粵語","seq_id":5,"abbr_en":"","channel_id":"6","name_en":""},{"name":"搖滾","seq_id":6,"abbr_en":"","channel_id":"7","name_en":""},{"name":"民謠","seq_id":7,"abbr_en":"","channel_id":"8","name_en":""},{"name":"輕音樂","seq_id":8,"abbr_en":"","channel_id":"9","name_en":""},{"name":"原聲","seq_id":9,"abbr_en":"","channel_id":"10","name_en":""},{"name":"Fly by midnight ","seq_id":10,"abbr_en":"","channel_id":"267","name_en":""},{"name":"獨立","seq_id":11,"abbr_en":"","channel_id":"268","name_en":""},{"name":"爵士","seq_id":12,"abbr_en":"","channel_id":"13","name_en":""},{"name":"電子","seq_id":13,"abbr_en":"","channel_id":"14","name_en":""},{"name":"說唱","seq_id":14,"abbr_en":"","channel_id":"15","name_en":""},{"name":"R&B ","seq_id":15,"abbr_en":"","channel_id":"16","name_en":""},{"name":"日語","seq_id":16,"abbr_en":"","channel_id":"17","name_en":""},{"name":"韓語","seq_id":17,"abbr_en":"","channel_id":"18","name_en":""},{"name":"我的巴比倫戀人","seq_id":18,"abbr_en":"","channel_id":"259","name_en":""},{"name":"女聲","seq_id":19,"abbr_en":"","channel_id":"20","name_en":""},{"name":"法語","seq_id":20,"abbr_en":"","channel_id":"22","name_en":""},{"name":"戶外","seq_id":21,"abbr_en":"","channel_id":"151","name_en":""},{"name":"休息","seq_id":22,"abbr_en":"","channel_id":"152","name_en":""},{"name":"工作學習","seq_id":23,"abbr_en":"","channel_id":"153","name_en":""},{"name":"亢奮","seq_id":24,"abbr_en":"","channel_id":"154","name_en":""},{"name":"古典","seq_id":25,"abbr_en":"","channel_id":"27","name_en":""},{"name":"動漫","seq_id":26,"abbr_en":"","channel_id":"28","name_en":""},{"name":"咖啡館","seq_id":27,"abbr_en":"","channel_id":"32","name_en":""},{"name":"舒緩","seq_id":28,"abbr_en":"","channel_id":"155","name_en":""},{"name":"18歲青春的召喚","seq_id":29,"abbr_en":"","channel_id":"262","name_en":""},{"name":"紅歌","seq_id":30,"abbr_en":"","channel_id":"41","name_en":""},{"name":"圣誕","seq_id":31,"abbr_en":"","channel_id":"170","name_en":""},{"name":"運動","seq_id":32,"abbr_en":"","channel_id":"257","name_en":""},{"name":"英語","seq_id":33,"abbr_en":"","channel_id":"264","name_en":""},{"name":"豆瓣好歌曲","seq_id":34,"abbr_en":"","channel_id":"179","name_en":""},{"name":"Future Pop","seq_id":35,"abbr_en":"","channel_id":"266","name_en":""},{"name":"金屬","seq_id":36,"abbr_en":"","channel_id":"187","name_en":""},{"name":"布魯斯","seq_id":37,"abbr_en":"","channel_id":"188","name_en":""},{"name":"新歌","seq_id":38,"abbr_en":"","channel_id":"61","name_en":""},{"name":"世界杯","seq_id":39,"abbr_en":"","channel_id":"201","name_en":""},{"name":"朋克","seq_id":40,"abbr_en":"","channel_id":"76","name_en":""},{"name":"Easy ","seq_id":41,"abbr_en":"","channel_id":"77","name_en":""},{"name":"91.1 ","seq_id":42,"abbr_en":"","channel_id":"78","name_en":""},{"name":"鄉村","seq_id":43,"abbr_en":"","channel_id":"269","name_en":""},{"name":"“磚”屬音樂","seq_id":44,"abbr_en":"","channel_id":"145","name_en":""},{"name":"Pop","seq_id":45,"abbr_en":"","channel_id":"194","name_en":""},{"name":"拉丁","seq_id":46,"abbr_en":"","channel_id":"189","name_en":""}]}

• 如果還要處理失敗的情況，可以在 onError 回調中操作：

// 創建URL對象 let urlString = "https://www.douban.com/xxxxxx/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.data(request: request).subscribe(onNext: {data inlet str = String(data: data, encoding: String.Encoding.utf8)print("請求成功！返回的數據是：", str ?? "") }, onError: { error inprint("請求失敗！錯誤原因：", error) }).disposed(by: disposeBag)

• 運行結果：

"https://www.douban.com/xxxxxx/app/radio/channels" -i -v Failure (7189ms): Status 404 請求失敗！錯誤原因： HTTP request failed with `404`.

二、手動發起請求和取消請求

• 在很多情況下，網絡請求并不是由程序自動發起的，可能需要我們點擊個按鈕，或者切換個標簽時才去請求數據。除了手動發起請求外，同樣的可能還需要手動取消上一次的網絡請求（如果未完成），那么 RxSwift 該如何實現呢？
• 如下所示：
• • 每次點擊“發起請求”按鈕則去請求一次數據；
• • 如果請求沒返回時，點擊“取消請求”則可將其取消（取消后即使返回數據也不作處理）。

//“發起請求”按鈕@IBOutlet weak var startBtn: UIButton!//“取消請求”按鈕@IBOutlet weak var cancelBtn: UIButton!let disposeBag = DisposeBag()override func viewDidLoad() {super.viewDidLoad()//創建URL對象let urlString = "https://www.douban.com/j/app/radio/channels"let url = URL(string:urlString)//創建請求對象let request = URLRequest(url: url!)//發起請求按鈕點擊startBtn.rx.tap.asObservable().flatMap {URLSession.shared.rx.data(request: request).takeUntil(self.cancelBtn.rx.tap) //如果“取消按鈕”點擊則停止請求}.subscribe(onNext: {data inlet str = String(data: data, encoding: String.Encoding.utf8)print("請求成功！返回的數據是：", str ?? "")}, onError: { error inprint("請求失敗！錯誤原因：", error)}).disposed(by: disposeBag)

三、將結果轉為 Json 對象

• 如果服務器返回的數據是 json 格式的話，可以使用 iOS 內置的 JSONSerialization 將其轉成 JSON 對象，方便使用：

// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.data(request: request).subscribe(onNext: {data inlet json = try? (JSONSerialization.jsonObject(with: data, options: .allowFragments)as! [String: Any])print("--- 請求成功，返回的如下數據 ---")print(json!) }).disposed(by: disposeBag)

• 運行結果如下：

"https://www.douban.com/j/app/radio/channels" -i -v Success (3410ms): Status 200 --- 請求成功！返回的如下數據 --- ["channels": <__NSArrayI 0x7ff0f2f07080>( {"abbr_en" = "";"channel_id" = 9;name = "\U8f7b\U97f3\U4e50";"name_en" = "";"seq_id" = 8; }, {"abbr_en" = "";"channel_id" = 10;name = "\U539f\U58f0";"name_en" = "";"seq_id" = 9; }, {"abbr_en" = "";"channel_id" = 267;name = "Fly by midnight ";"name_en" = "";"seq_id" = 10; }, {"abbr_en" = "";"channel_id" = 268;name = "\U72ec\U7acb";"name_en" = "";"seq_id" = 11; }, {"abbr_en" = "";"channel_id" = 13;name = "\U7235\U58eb";"name_en" = "";"seq_id" = 12; }, {"abbr_en" = "";"channel_id" = 14;name = "\U7535\U5b50";"name_en" = "";"seq_id" = 13; }, {"abbr_en" = "";"channel_id" = 15;name = "\U8bf4\U5531";"name_en" = "";"seq_id" = 14; }, {"abbr_en" = "";"channel_id" = 16;name = "R&B ";"name_en" = "";"seq_id" = 15; }, {"abbr_en" = "";"channel_id" = 17;name = "\U65e5\U8bed";"name_en" = "";"seq_id" = 16; }, {"abbr_en" = "";"channel_id" = 18;name = "\U97e9\U8bed";"name_en" = "";"seq_id" = 17; }, {"abbr_en" = "";"channel_id" = 259;name = "\U6211\U7684\U5df4\U6bd4\U4f26\U604b\U4eba";"name_en" = "";"seq_id" = 18; }, {"abbr_en" = "";"channel_id" = 20;name = "\U5973\U58f0";"name_en" = "";"seq_id" = 19; }, {"abbr_en" = "";"channel_id" = 22;name = "\U6cd5\U8bed";"name_en" = "";"seq_id" = 20; }, {"abbr_en" = "";"channel_id" = 151;name = "\U6237\U5916";"name_en" = "";"seq_id" = 21; }, {"abbr_en" = "";"channel_id" = 152;name = "\U4f11\U606f";"name_en" = "";"seq_id" = 22; }, {"abbr_en" = "";"channel_id" = 28;name = "\U52a8\U6f2b";"name_en" = "";"seq_id" = 26; }, {"abbr_en" = "";"channel_id" = 32;name = "\U5496\U5561\U9986";"name_en" = "";"seq_id" = 27; }, {"abbr_en" = "";"channel_id" = 155;name = "\U8212\U7f13";"name_en" = "";"seq_id" = 28; }, {"abbr_en" = "";"channel_id" = 262;name = "18\U5c81\U9752\U6625\U7684\U53ec\U5524";"name_en" = "";"seq_id" = 29; }, {"abbr_en" = "";"channel_id" = 41;name = "\U7ea2\U6b4c";"name_en" = "";"seq_id" = 30; }, {"abbr_en" = "";"channel_id" = 170;name = "\U5723\U8bde";"name_en" = "";"seq_id" = 31; }, {"abbr_en" = "";"channel_id" = 257;name = "\U8fd0\U52a8";"name_en" = "";"seq_id" = 32; }, {"abbr_en" = "";"channel_id" = 264;name = "\U82f1\U8bed";"name_en" = "";"seq_id" = 33; }, {"abbr_en" = "";"channel_id" = 179;name = "\U8c46\U74e3\U597d\U6b4c\U66f2";"name_en" = "";"seq_id" = 34; } ) ]

• 也可以在訂閱前就進行轉換：

// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.data(request: request).map {try JSONSerialization.jsonObject(with: $0, options: .allowFragments)as! [String: Any]}.subscribe(onNext: {data inprint("--- 請求成功！返回的如下數據 ---")print(data)}).disposed(by: disposeBag)

• 還有更簡單的方法，就是直接使用 RxSwift 提供的 rx.json 方法去獲取數據，它會直接將結果轉成 Json 對象：

// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.json(request: request).subscribe(onNext: {data inlet json = data as! [String: Any]print("--- 請求成功！返回的如下數據 ---")print(json ) }).disposed(by: disposeBag)

• 將獲取到的豆瓣頻道列表數據轉換成 Json 對象，并綁定到表格上顯示：

// 創建表格視圖 self.tableView = UITableView(frame: self.view.frame, style:.plain) // 創建一個重用的單元格 self.tableView!.register(UITableViewCell.self, forCellReuseIdentifier: "Cell") self.view.addSubview(self.tableView!)// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 獲取列表數據 let data = URLSession.shared.rx.json(request: request).map{ result -> [[String: Any]] inif let data = result as? [String: Any],let channels = data["channels"] as? [[String: Any]] {return channels}else{return []} }// 將數據綁定到表格 data.bind(to: tableView.rx.items) { (tableView, row, element) inlet cell = tableView.dequeueReusableCell(withIdentifier: "Cell")!cell.textLabel?.text = "\(row)：\(element["name"]!)"return cell }.disposed(by: disposeBag)

• 效果如下：

四、將結果映射成自定義對象

① 準備工作

• 要實現數據到模型（model）的轉換，首先需要引入一個第三方的數據模型轉換框架：ObjectMapper。
• 為了讓 ObjectMapper 能夠更好地與 RxSwift 配合使用，對 Observable 進行擴展（RxObjectMapper.swift），增加數據轉模型對象、以及數據轉模型對象數組這兩個方法：

import ObjectMapper import RxSwift// 數據映射錯誤 public enum RxObjectMapperError: Error {case parsingError }// 擴展Observable：增加模型映射方法 public extension Observable where Element:Any {// 將Json數據轉成對象public func mapObject< T>(type:T.Type) -> Observable<T> where T:Mappable {let mapper = Mapper<T>()return self.map { (element) -> T inguard let parsedElement = mapper.map(JSONObject: element) else {throw RxObjectMapperError.parsingError}return parsedElement}}// 將Json數據轉成數組public func mapArray< T>(type:T.Type) -> Observable<[T]> where T:Mappable {let mapper = Mapper<T>()return self.map { (element) -> [T] inguard let parsedArray = mapper.mapArray(JSONObject: element) else {throw RxObjectMapperError.parsingError}return parsedArray}} }

② 使用示例

• 以豆瓣音樂頻道數據為例，首先定義好相關模型（需要實現 ObjectMapper 的 Mappable 協議，并設置好成員對象與 Json 屬性的相互映射關系）：

// 豆瓣接口模型 class Douban: Mappable {// 頻道列表var channels: [Channel]?init(){}required init?(map: Map) {}// Mappablefunc mapping(map: Map) {channels <- map["channels"]} }// 頻道模型 class Channel: Mappable {var name: String?var nameEn:String?var channelId: String?var seqId: Int?var abbrEn: String?init(){}required init?(map: Map) {}// Mappablefunc mapping(map: Map) {name <- map["name"]nameEn <- map["name_en"]channelId <- map["channel_id"]seqId <- map["seq_id"]abbrEn <- map["abbr_en"]} }

• 如下所示，獲取數據，并轉換成對應的模型：

// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 創建并發起請求 URLSession.shared.rx.json(request: request).mapObject(type: Douban.self).subscribe(onNext: { (douban: Douban) inif let channels = douban.channels {print("--- 共\(channels.count)個頻道 ---")for channel in channels {if let name = channel.name, let channelId = channel.channelId {print("\(name) （id:\(channelId)）")}}}}).disposed(by: disposeBag)

• 如下所示，將數據換成模型，并綁定到表格上顯示：

// 創建表格視圖 self.tableView = UITableView(frame: self.view.frame, style:.plain) // 創建一個重用的單元格 self.tableView!.register(UITableViewCell.self, forCellReuseIdentifier: "Cell") self.view.addSubview(self.tableView!)// 創建URL對象 let urlString = "https://www.douban.com/j/app/radio/channels" let url = URL(string:urlString) // 創建請求對象 let request = URLRequest(url: url!)// 獲取列表數據 let data = URLSession.shared.rx.json(request: request).mapObject(type: Douban.self).map{ $0.channels ?? []}// 將數據綁定到表格 data.bind(to: tableView.rx.items) { (tableView, row, element) inlet cell = tableView.dequeueReusableCell(withIdentifier: "Cell")!cell.textLabel?.text = "\(row)：\(element.name!)"return cell }.disposed(by: disposeBag)

總結

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