基於Moya、RxSwift和ObjectMapper優雅實現REST API請求

在Android開發中有非常強大的 Retrofit 請求，結合RxJava可以非常方便實現 RESTful API 網路請求。在 iOS開發中也有非常強大的網路請求庫 Moya ，Moya是一個基於 Alamofire 開發的,輕量級的Swift網路層。Moya的可擴展性非常強,可以方便和RXSwift、ObjectMapper結合。

測試 REST API 定義

我們先用服務端定義幾個REST API，開發者根據自己的條件來實現。

請求錯誤格式實例

{
    "error": "密碼錯誤",
    "error_code": "password_error"
}

測試 API 列表

1. http://127.0.0.1:8080/account/login，參數username、password，post請求，成功響應為User。
2. http://127.0.0.1:8080/user/{userId}，get請求，成功響應為User。
3. http://127.0.0.1:8080/user/query?q={keyword}，get請求，成功響應為User列表。

創建介面

// MyApiService.swift
import Moya

enum MyApiService {
    case login(username:String,password:String)
    case user(userId:String)
    case userQuery(keyword:String)
}
extension MyApiService:TargetType{
    // 定義請求的host
    var baseURL: URL {
        return URL(string: "http://127.0.0.1:8080")!
    }
    // 定義請求的路徑
    var path: String {
        switch self {
        case .login(_, _):
            return "/account/login"
        case .user(let userId):
            return "user/\(userId)"
        case .userQuery(_):
            return "user/query"
        }
    }
    // 定義介面請求方式
    var method: Moya.Method {
        switch self {
        case .login:
            return .post
        case .user,.userQuery:
            return .get
        }
    }
    // 定義模擬數據
    var sampleData: Data {
        switch self {
        case .login(let username, _):
            return "{\"username\": \"\(username)\", \"id\": 100}".data(using: String.Encoding.utf8)!
        case .user(_):
            return "{\"username\": \"Wiki\", \"id\": 100}".data(using: String.Encoding.utf8)!
        case .userQuery(_):
            return "{\"username\": \"Wiki\", \"id\": 100}".data(using: String.Encoding.utf8)!
        }
    }
    // 構建參數
    var task: Task {
        switch self {
        case .login(let username, let passowrd):
            return .requestParameters(parameters: ["username": username,"passowrd": passowrd], encoding: URLEncoding.default)
        case .user(_):
            return .requestPlain
        case .userQuery(let keyword):
            return .requestParameters(parameters: ["keyword": keyword], encoding: URLEncoding.default)
        }
    }
    // 構建請求頭部
    var headers: [String : String]? {
        return ["Content-type": "application/json"]
    }
}

請求數據

let provider = MoyaProvider<MyApiService>()

// Moya 提供最原始的請求方式，響應的數據是二進位
provider.request(.user(userId: "101")){ result in
        // do something with the result
        let text = String(bytes: result.value!.data, encoding: .utf8)
    print("text1 = \(text)")
}

// 結合RxSwift，響應的數據是二進位
provider.rx.request(.user(userId: "101")).subscribe({result in
        // do something with the result
        switch result {
        case let .success(response):
            let text = String(bytes: response.data, encoding: .utf8)
            print("text2 = \(text)")
        case let .error(error):
            print(error)
    }
})

// 通過mapJSON把數據轉換成json格式
provider.rx.request(.user(userId: "101")).mapJSON().subscribe({result in
        // do something with the result
        switch result {
        case let .success(text):
            print("text3 = \(text)")
        case let .error(error):
            print(error)
    }
})
// 通過mapJSON把數據轉換成json格式，並轉換成最常見的Observable
provider.rx.request(.user(userId: "101")).mapJSON().asObservable().subscribe(onNext: { result in
        // do something with the result
        print("text4 = \(result)")
}, onError:{ error in
    // do something with the error
})

請求數據：RxBlocking

RxBlocking使用教程 ，可以使用同步的方式請求網路

import RxBlocking

do{
    let text = try provider.rx.request(.user(userId: "101")).mapJSON().toBlocking().first()
    print("text5 = \(text)")
}catch{
    print(error)
}

結合 ObjectMapper

引入ObjectMapper

pod 'ObjectMapper', '~> 3.4'

編寫RxSwift拓展代碼

//  MoyaRxSwiftObjectMapperExtension.swift

import Foundation
import RxSwift
import Moya
import ObjectMapper

public extension PrimitiveSequence where TraitType == SingleTrait, ElementType == Response {
    func mapObject<T: BaseMappable>(type: T.Type) -> Single<T> {
        return self.map{ response in
            return try response.mapObject(type: type)
        }
    }
    func mapArray<T: BaseMappable>(type: T.Type) -> Single<[T]> {
        return self.map{ response in
            return try response.mapArray(type: type)
        }
    }
}
public extension ObservableType where E == Response {
    func mapObject<T: BaseMappable>(type: T.Type) -> Observable<T> {
        return self.map{ response in
            return try response.mapObject(type: type)
        }
    }
    func mapArray<T: BaseMappable>(type: T.Type) -> Observable<[T]> {
        return self.map{ response in
            return try response.mapArray(type: type)
        }
    }
}

public extension Response{
    func mapObject<T: BaseMappable>(type: T.Type) throws -> T{
        let text = String(bytes: self.data, encoding: .utf8)
        if self.statusCode < 400 {
            return Mapper<T>().map(JSONString: text!)!
        }
        do{
            let serviceError = Mapper<ServiceError>().map(JSONString: text!)
            throw serviceError!
        }catch{
            if error is ServiceError {
                throw error
            }
            let serviceError = ServiceError()
            serviceError.message = "伺服器開小差，請稍後重試"
            serviceError.error_code = "parse_error"
            throw serviceError
        }
    }
    func mapArray<T: BaseMappable>(type: T.Type) throws -> [T]{
        let text = String(bytes: self.data, encoding: .utf8)
        if self.statusCode < 400 {
            return Mapper<T>().mapArray(JSONString: text!)!
        }
        do{
            let serviceError = Mapper<ServiceError>().map(JSONString: text!)
            throw serviceError!
        }catch{
            if error is ServiceError {
                throw error
            }
            let serviceError = ServiceError()
            serviceError.message = "伺服器開小差，請稍後重試"
            serviceError.error_code = "parse_error"
            throw serviceError
        }
    }
}
class ServiceError:Error,Mappable{
    var message:String = ""
    var error_code:String = ""
    required init?(map: Map) {}
    init() {
        
    }
    func mapping(map: Map) {
        error_code <- map["error_code"]
        message <- map["error"]
    }
    var localizedDescription: String{
        return message
    }
}

創建 User 類

//  User.swift
import ObjectMapper
class User: Mappable {
    required init?(map: Map) {}
    
    func mapping(map: Map) {
        userId <- map["userId"]
        name <- map["name"]
        age <- map["age"]
    }
    
    var userId:Int = 0
    var name:String = ""
    var age:Int = 0
}

測試

do{
    let user = try provider.rx.request(.user(userId: "101")).mapObject(type: User.self).toBlocking().first()
    print("user.name = \(user?.name)")
}catch{
    print(error)
}
do{
    let user = try provider.rx.request(.user(userId: "101")).asObservable().mapObject(type: User.self).toBlocking().first()
    print("user.name = \(user?.name)")
}catch{
    print(error)
}

do{
    let users = try provider.rx.request(.userQuery(keyword: "Wiki")).mapArray(type: User.self).toBlocking().first()
    print("test8 users.count = \(users?.count)")
}catch{
    if error is ServiceError {
        print((error as! ServiceError).message)
    }
    print(error)
}

列印日誌

private func JSONResponseDataFormatter(_ data: Data) -> Data {
    do {
        let dataAsJSON = try JSONSerialization.jsonObject(with: data)
        let prettyData =  try JSONSerialization.data(withJSONObject: dataAsJSON, options: .prettyPrinted)
        return prettyData
    } catch {
        return data // fallback to original data if it can't be serialized.
    }
}

let provider = MoyaProvider<MyApiService>(plugins: [NetworkLoggerPlugin(verbose: true, responseDataFormatter: JSONResponseDataFormatter)])