基于Moya、RxSwift和ObjectMapper优雅实现REST API请求

在Android开发中有非常强大的 Retrofit 请求，结合RxJava可以非常方便实现 RESTful API 网络请求。在 iOS开发中也有非常强大的网络请求库 Moya ，Moya是一个基于 Alamofire 开发的,轻量级的Swift网络层。Moya的可扩展性非常强,可以方便和RXSwift、ObjectMapper结合。

测试 REST API 定义

我们先用服务端定义几个REST API，开发者根据自己的条件来实现。

请求错误格式实例

{
    "error": "密码错误",
    "error_code": "password_error"
}

测试 API 列表

1. http://127.0.0.1:8080/account/login，参数username、password，post请求，成功响应为User。
2. http://127.0.0.1:8080/user/{userId}，get请求，成功响应为User。
3. http://127.0.0.1:8080/user/query?q={keyword}，get请求，成功响应为User列表。

创建接口

// MyApiService.swift
import Moya
enum MyApiService {
    case login(username:String,password:String)
    case user(userId:String)
    case userQuery(keyword:String)
}
extension MyApiService:TargetType{
    // 定义请求的host
    var baseURL: URL {
        return URL(string: "http://127.0.0.1:8080")!
    }
    // 定义请求的路径
    var path: String {
        switch self {
        case .login(_, _):
            return "/account/login"
        case .user(let userId):
            return "user/\(userId)"
        case .userQuery(_):
            return "user/query"
        }
    }
    // 定义接口请求方式
    var method: Moya.Method {
        switch self {
        case .login:
            return .post
        case .user,.userQuery:
            return .get
        }
    }
    // 定义模拟数据
    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)!
        }
    }
    // 构建参数
    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)
        }
    }
    // 构建请求头部
    var headers: [String : String]? {
        return ["Content-type": "application/json"]
    }
}

请求数据

let provider = MoyaProvider<MyApiService>()
// Moya 提供最原始的请求方式，响应的数据是二进制
provider.request(.user(userId: "101")){ result in
        // do something with the result
        let text = String(bytes: result.value!.data, encoding: .utf8)
    print("text1 = \(text)")
}
// 结合RxSwift，响应的数据是二进制
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)
    }
})
// 通过mapJSON把数据转换成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)
    }
})
// 通过mapJSON把数据转换成json格式，并转换成最常见的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
})

请求数据：RxBlocking

RxBlocking使用教程 ，可以使用同步的方式请求网络

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

结合 ObjectMapper

引入ObjectMapper

pod 'ObjectMapper', '~> 3.4'

编写RxSwift拓展代码

//  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 = "服务器开小差，请稍后重试"
            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 = "服务器开小差，请稍后重试"
            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
    }
}

创建 User 类

//  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
}

测试

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)
}

打印日志

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)])