一.前言

對于iOS開發(fā)者，應(yīng)該沒有不知道AFNetworking的！它是一個用OC語言寫的網(wǎng)絡(luò)庫，對于AFNetworking有很多著名的二次封裝，比如猿題庫團(tuán)隊(duì)的開源庫YTKNetwork，它將AFNetworking封裝成抽象父類，然后根據(jù)每個不同的網(wǎng)絡(luò)請求，都編寫不同的子類，子類繼承父類，來實(shí)現(xiàn)請求業(yè)務(wù)（OOP思想設(shè)計(jì)）。

對于Swift開發(fā)，優(yōu)雅的網(wǎng)絡(luò)開發(fā)框架Alamofire當(dāng)是不二選擇，Alamofire是建立在NSURLSession上的封裝，可以直接使用Alamofire進(jìn)行網(wǎng)絡(luò)請求，但是我們項(xiàng)目中往往需要一些“項(xiàng)目化”設(shè)置，所以習(xí)慣二次封裝。在Swift開源社區(qū)，對Alamofire二次封裝最有名的當(dāng)屬Moya，它在底層將Alamofire進(jìn)行封裝，對外提供更簡潔的接口供開發(fā)者調(diào)用(POP思想設(shè)計(jì)).

Alamofire地址: https://github.com/Alamofire/Alamofire
Moya地址: https://github.com/Moya/Moya

不過似乎在大型項(xiàng)目，比如使用Moya+RxSwift+MVVM才能發(fā)揮Moya的威力，所以對中小項(xiàng)目，大都會自己簡單對Alamofire封裝下使用，網(wǎng)上搜索一下，封裝之后的使用方法幾乎都是下面這種方式:

NetworkTools.request(url: "api", parameters:p, success: { (response) in
    // TODO...
}) { (error) in
    // TODO...
}

這種應(yīng)該是受OC的影響，方法里面跟著2個Block回調(diào)的思路。但在Swift里面就是兩個逃逸尾隨閉包@escaping closure，雖然語法沒問題，但是我感覺怪怪的，特別是閉包里面代碼一多起來，{()}{()}大括號看的暈暈的。

我受PromiseKit和JQuery啟發(fā)，進(jìn)行了點(diǎn)語法封裝，使用方法如下:

PromiseKit是iOS/MacOS中一個用來處理異步編程的框架。可以直接配合Alamofire或者AFNetworking進(jìn)行處理，功能很強(qiáng)大!
GitHub: https://github.com/mxcl/PromiseKit

二.使用方法A

// 進(jìn)行一個請求，不管失敗情況
HN.POST(url: url, parameters: p, datas: datas).success { (response) in
    debugPrint("success: \(response)")
}

// 進(jìn)行一個請求，處理成功和失敗
HN.GET(url: url, parameters: p).success { (response) in
    debugPrint("success: \(response)")
}.failed { (error) in
    debugPrint("failed: \(error)")
}

// 上傳圖片
HN.POST(url: url, parameters: p, datas: datas).progress { (progress) in
    debugPrint("progress: \(progress.fractionCompleted)")
}.success { (response) in
    debugPrint("success: \(response)")
}.failed { (error) in
    debugPrint("failed: \(error)")
}

正如上面代碼所示，成功和失敗都是使用點(diǎn)語法進(jìn)行回調(diào)，清晰明了，甚至你可以不管成功和失敗，只發(fā)送一個請求:

HN.GET(url: "api")

三.使用方法B

3.1 結(jié)合HWAPIProtocol使用，這里新建一個struct去實(shí)現(xiàn)HWAPIProtocol:

struct APIItem: HWAPIProtocol {
    var url: String { API.DOMAIN + URLPath }  // 域名 + path
    let description: String
    let extra: String?
    var method: HWHTTPMethod

    private let URLPath: String  // URL的path

    init(_ path: String, d: String, e: String? = nil, m: HWHTTPMethod = .get) {
        URLPath = path
        description = d
        extra = e
        method = m
    }
}

3.2. 項(xiàng)目里面，寫API的文件就可以設(shè)計(jì)為(模塊化):

struct API {
    static var DOMAIN = "https://www.baidu.com/"

    // MARK: Home模塊
    struct Home {
        static let homeIndex = APIItem("homeIndex", d: "首頁數(shù)據(jù)")
        static let storeList = APIItem("homeIndex", d: "首頁門店列表", m: .post)
    }

    // MARK: 圈子模塊
    struct Social {
        static let socialIndex = APIItem("socialList", d: "圈子首頁列表")
    }
}

3.3 網(wǎng)絡(luò)請求方式:

// 1.不帶參數(shù)
HN.fetch(API.Home.homeIndex).success { response in
    print(response)
}

// 2.加上參數(shù)
let p: [String: Any] = ["name": "ZhangSan", "age": 22]
HN.fetch(API.Home.homeIndex, parameters: p).success { response in
    print(response)
}

// 3.加上Header 和失敗情況
let h = ["Referrer Policy": "no-referrer-when-downgrade"]
HN.fetch(API.Home.homeIndex, headers: h).success { response in
    print(response)
}.failed { error in
    print(error)
}

可能有人疑問，為什么接口要加一個description，這里解釋一下:
1.在API文件里，能直接明白這接口是做什么的
2.在我項(xiàng)目里，有一個debug隱藏模塊，可以看到所有的API請求情況，可以看到這個description
3.在debug模塊里，不僅后臺Java同事能通過description定位接口，測試同事也方便找接口

四.使用方法C

由于已經(jīng)為HWAPIProtocol擴(kuò)展了已實(shí)現(xiàn)fetch()方法，所以上面的請求可以簡化為更高階的方式:

// 1.不帶參數(shù)
API.Me.meIndex.fetch().success { response in
    print("response -->", response)
}.failed { error in
    print("error -->", error)
}

API.Home.homeIndex.fetch(success: {response in
    print(response)
}, failed: {error in
    print(error)
})

// 2.加上參數(shù)
let p: [String: Any] = ["name": "ZhangSan", "age": 22]
API.Home.homeIndex.fetch(p, success: { response in
    print(response)
}) { error in
    print(error)
}

// 3.加上Header 和失敗情況
let h = ["Referrer Policy": "no-referrer-when-downgrade"]
API.Home.homeIndex.fetch(p, headers: h, success: { response in
    print(response)
}) { error in
    print(error)
}

五.OC使用方法

OC的請求如下，具體可以看Demo，這里簡單列舉一個實(shí)例：

NSString *url = @"http://game.gtimg.cn/images/lol/act/img/js/heroList/hero_list.js";
NSDictionary *dict = @{@"v": @(33)};

[HWNetworkingOC GET:url info:@"LOL英雄列表" parameters:dict success:^(id response) {
    NSLog(@"%@", response);
} failed:^(NSString *error) {
    NSLog(@"%@", error);
}];

六.思路？

設(shè)計(jì)思路其實(shí)很簡單，首先是一個單例，用于持有Alamofire.Session和每個請求對象，順便定義幾個回調(diào)

/// Closure type executed when the request is successful
public typealias HNSuccessClosure = (_ JSON: Any) -> Void
/// Closure type executed when the request is failed
public typealias HNFailedClosure = (_ error: Any) -> Void
/// Closure type executed when monitoring the upload or download progress of a request.
public typealias HNProgressHandler = (Progress) -> Void

public class HWNetworking {
    /// For singleton pattern
    public static let shared = HWNetworking()
    /// TaskQueue Array for (`Alamofire.Request` & callback)
    private var taskQueue = [HWNetworkRequest]()
    /// `Session` creates and manages Alamofire's `Request` types during their lifetimes.
    var sessionManager: Alamofire.Session!
}

把每個請求封裝成對象，調(diào)用對象的success(...)方法和failed(...)等，獲得這個請求的成功和失敗回調(diào)，回調(diào)之后，銷毀對象即可.

public class HWNetworkRequest: Equatable {
    /// Alamofire.DataRequest
    var request: DataRequest?
    
    /// request response callback
    private var successHandler: HNSuccessClosure?
    /// request failed callback
    private var failedHandler: HNFailedClosure?
    /// `ProgressHandler` provided for upload/download progress callbacks.
    private var progressHandler: HNProgressHandler?

    // MARK: - Handler
    
    /// Handle request response
    func handleResponse(response: AFDataResponse<Any>) {
        switch response.result {
        case .failure(let error):
            if let closure = failedHandler  {
                closure(error.localizedDescription)
            }
   
        case .success(let JSON):
            if let closure = successHandler  {
                closure(JSON)
            }
        }
        clearReference()
    }
    
    /// Processing request progress (Only when uploading files)
    func handleProgress(progress: Foundation.Progress) {
        if let closure = progressHandler  {
            closure(progress)
        }
    }
    
    // MARK: - Callback
    
    /// Adds a handler to be called once the request has finished.
    public func success(_ closure: @escaping HNSuccessClosure) -> Self {
        successHandler = closure
        return self
    }
    
    /// Adds a handler to be called once the request has finished.
    @discardableResult
    public func failed(_ closure: @escaping HNFailedClosure) -> Self {
        failedHandler = closure
        return self
    }
}

核心的請求方法如下：

extension HWNetworking {
    public func request(url: String,
                        method: HTTPMethod = .get,
                        parameters: [String: Any]?,
                        headers: [String: String]? = nil,
                        encoding: ParameterEncoding = URLEncoding.default) -> HWNetworkRequest {
        let task = HWNetworkRequest()
        
        var h: HTTPHeaders? = nil
        if let tempHeaders = headers {
            h = HTTPHeaders(tempHeaders)
        }
        
        task.request = sessionManager.request(url,
                                              method: method,
                                              parameters: parameters,
                                              encoding: encoding,
                                              headers: h).validate().responseJSON { [weak self] response in
            task.handleResponse(response: response)
            
            if let index = self?.taskQueue.firstIndex(of: task) {
                self?.taskQueue.remove(at: index)
            }
        }
        taskQueue.append(task)
        return task
    }
}

再封裝幾個常用的POST和Get快捷方法：

/// Shortcut method for `HWNetworking`
extension HWNetworking {
    @discardableResult
    public func POST(url: String, parameters: [String: Any]? = nil, headers: [String: String]? = nil) -> HWNetworkRequest {
        request(url: url, method: .post, parameters: parameters, headers: nil)
    }

    /// Creates a GET request
    @discardableResult
    public func GET(url: String, parameters: [String: Any]? = nil, headers: [String: String]? = nil) -> HWNetworkRequest {
        request(url: url, method: .get, parameters: parameters, headers: nil)
    }
}

大致的思路就如上面貼出的關(guān)鍵代碼，限于篇幅，這里不貼完整的代碼了，可以直接去Github上clone下來看看，實(shí)現(xiàn)的大致功能如下:

• 常規(guī)的POST/GET
• 網(wǎng)絡(luò)狀態(tài)監(jiān)聽和通知
• 上傳圖片的封裝(單張或者多張)
• 下載文件(沒有做，我這項(xiàng)目里沒有這樣的需求，不過方法留著了，自行擴(kuò)展即可)

將來要做的功能:

• 支持closure和delegate兩種模式的回調(diào)方式
• 支持網(wǎng)絡(luò)請求URL的filter，可以統(tǒng)一為網(wǎng)絡(luò)請求加上一些參數(shù)，或者攔截請求結(jié)果
• 統(tǒng)一的Header設(shè)置

也歡迎大家把好的想法留言或者git Issues，因?yàn)槲視陧?xiàng)目里使用這個類，所以后面如果有新的想法和功能，我都會更新維護(hù)的。

Github地址，GitHub點(diǎn)我或者復(fù)制下面鏈接：
https://github.com/HouWan/HWNetworking

從github上clone下以后，cd到目錄SwiftDemo，執(zhí)行pod install命令即可運(yùn)行Demo

關(guān)于尾隨閉包，可能有同學(xué)說，那系統(tǒng)很多API這么使用的，比如:

UIView.animate(withDuration: 1, animations: {
    // TODO...
}) { (finished) in
    // TODO...
}

這個看大家習(xí)慣了，不過在最新的Swift 5.3中，針對這塊多個尾隨閉包有了新的語法糖：

// old Swift3
UIView.animate(withDuration: 0.3, animations: {
    self.view.alpha = 0
}, completion: { _ in
    self.view.removeFromSuperview()
})
// still old  Swift4/5
UIView.animate(withDuration: 0.3, animations: {
    self.view.alpha = 0
}) { _ in
    self.view.removeFromSuperview()
}
// new swift 5.3
UIView.animate(withDuration: 0.3) {
    self.view.alpha = 0
} completion: { _ in
    self.view.removeFromSuperview()
}

END。
我是小侯爺。
在帝都艱苦奮斗，白天是上班族，晚上是知識服務(wù)工作者。
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