ReactiveX 学习笔记（17）使用 RxSwift + Alamofire 调用 REST API

JSON : Placeholder

JSON : Placeholder (https://jsonplaceholder.typicode.com/) 是一个用于测试的 REST API 网站。
以下使用 RxSwift + Alamofire 调用该网站的 REST API，获取字符串以及 JSON 数据。

• GET /posts/1
• GET /posts
• POST /posts
• PUT /posts/1
• DELETE /posts/1

所有 GET API 都返回JSON数据，格式（JSON-Schema）如下：

{
  "type":"object",
  "properties": {
    "userId": {"type" : "integer"},
    "id": {"type" : "integer"},
    "title": {"type" : "string"},
    "body": {"type" : "string"}
  }
}

创建工程

打开 Xcode，File / New / Project..
在 New Project 向导的第1页，选 iOS / Single View App
在向导的第2页填上 Product Name: RxExample
在向导的第3页选择任意文件夹点击 Create 按钮创建工程
关闭所创建的工程

配置 Pods

在工程所在文件夹下创建 Podfile 文件，内容如下：

workspace 'RxExample'

use_frameworks!

target 'RxExample' do
project 'RxExample'
pod 'CodableAlamofire'
pod 'RxAlamofire'
end

打开终端在工程所在文件夹下执行 pod install 命令。

$ cd RxExample
$ pod install
...
Installing Alamofire (4.7.3)
Installing CodableAlamofire (1.1.0)
Installing RxAlamofire (4.2.0)
Installing RxSwift (4.2.0)
...

用 Xcode 打开 RxExample.xcworkspace

RxCodableAlamofire

在 RxExample 工程中添加 RxCodableAlamofire.swift 文件，内容如下：

import Foundation
import RxSwift
import Alamofire
import RxAlamofire
import CodableAlamofire

class RxCodableAlamofire {
    public static func object<T: Decodable>(_ method: Alamofire.HTTPMethod, _ url: URLConvertible, parameters: [String: Any]? = nil, encoding: ParameterEncoding = URLEncoding.default, headers: [String: String]? = nil, queue: DispatchQueue? = nil, keyPath: String? = nil, mapToObject object: T? = nil, decoder: JSONDecoder = JSONDecoder()) -> Observable<T> {
        return SessionManager.default.rx.object(method, url, parameters: parameters, encoding: encoding, headers: headers, queue: queue, keyPath: keyPath, mapToObject: object, decoder: decoder)
    }
}

extension Reactive where Base: SessionManager {
    public func object<T: Decodable>(_ method: Alamofire.HTTPMethod, _ url: URLConvertible, parameters: [String: Any]? = nil, encoding: ParameterEncoding = URLEncoding.default, headers: [String: String]? = nil, queue: DispatchQueue? = nil, keyPath: String? = nil, mapToObject object: T? = nil, decoder: JSONDecoder = JSONDecoder()) -> Observable<T> {
        return request(method, url, parameters: parameters, encoding: encoding, headers: headers).flatMap { $0.rx.object(queue: queue, keyPath: keyPath, mapToObject: object, decoder: decoder) }
    }
}

extension Reactive where Base: DataRequest {
    public func object<T: Decodable>(queue: DispatchQueue? = nil, keyPath: String? = nil, mapToObject object: T? = nil, decoder: JSONDecoder = JSONDecoder()) -> Observable<T> {
        return result(queue: queue, responseSerializer: DataRequest.DecodableObjectSerializer(keyPath, decoder))
    }
}

在 Pods 工程中找到并打开 DataRequest+Decodable.swift （Pods/CodableAlamofire）
将其中的 DecodableObjectSerializer 的可见性从 private 改为 public。(提示是否 unlock 时按下 Unlock)

RestApi

在 RxExample 工程中添加 RestApi.swift 文件，内容如下：

import Foundation
import Alamofire
import RxSwift
import RxAlamofire

// https://stackoverflow.com/questions/27855319/post-request-with-a-simple-string-in-body-with-alamofire
class StringEncoding: ParameterEncoding {
    let body: String;
    
    public init(body: String) {
        self.body = body
    }
    
    public func encode(_ urlRequest: URLRequestConvertible, with parameters: Parameters?) throws -> URLRequest {
        var request = try urlRequest.asURLRequest()
        request.httpBody = body.data(using: .utf8, allowLossyConversion: false)
        return request
    }
}

extension Encodable {
    
    public func toJSONString(prettyPrint: Bool) throws -> String? {
        let encoder = JSONEncoder()
        if prettyPrint { encoder.outputFormatting = .prettyPrinted }
        let data = try! encoder.encode(self)
        let jsonString = String(data: data, encoding: .utf8)
        return jsonString
    }
    
}

class RestApi {
    static func getObject<T: Decodable>(url: String, keyPath: String? = nil) -> Observable<T> {
        return RxCodableAlamofire.object(.get, url, keyPath: keyPath)
    }
    static func getArray<T: Decodable>(url: String, keyPath: String? = nil) -> Observable<[T]> {
        return RxCodableAlamofire.object(.get, url, keyPath: keyPath)
    }
    static func update(url: String, body: String) -> Observable<String> {
        return RxAlamofire.string(.put, url, encoding: StringEncoding(body: body))
    }
    static func create(url: String, body: String) -> Observable<String> {
        return RxAlamofire.string(.post, url, encoding: StringEncoding(body: body))
    }
    static func delete(url: String) -> Observable<String> {
        return RxAlamofire.string(.delete, url)
    }
    static func getString(url: String) -> Observable<String> {
        return RxAlamofire.string(.get, url)
    }
}

Post

在 RxExample 工程中添加 Post.swift 文件，内容如下：

import Foundation
import RxSwift

struct Post : Codable {
    let userId: Int
    let id: Int
    let title: String
    let body: String
    var description: String {
        return "Post {userId = (userId), id = (id), title = "(title)", body = "(body.replacingOccurrences(of: "
", with: "\n"))"}";
    }
    
    static let url = "https://jsonplaceholder.typicode.com/"

    static func getPostAsString() -> Observable<String> {
        return RestApi.getString(url: "(url)posts/1")
    }
    static func getPostAsJson() -> Observable<Post> {
        return RestApi.getObject(url: "(url)posts/1")
    }
    static func getPosts(n: Int) -> Observable<Post> {
        return RestApi.getArray(url: "(url)posts").flatMap { Observable.from($0) }.take(n)
    }
    static func createPost() -> Observable<String> {
        let post = Post(userId: 101, id: 0, title: "test title", body: "test body")
        return RestApi.create(url: "(url)posts", body: try! post.toJSONString(prettyPrint: false)!)
    }
    static func updatePost() -> Observable<String> {
        let post = Post(userId: 101, id: 1, title: "test title", body: "test body")
        return RestApi.update(url: "(url)posts/1", body: try! post.toJSONString(prettyPrint: false)!)
    }
    static func deletePost() -> Observable<String> {
        return RestApi.delete(url: "(url)posts/1")
    }
}

• getPostAsString 方法取出第1个Post，返回字符串
• getPostAsJson 方法取出第1个Post，返回Post对象
• getPosts 方法取出前n个Post，返回n个Post对象
• createPost 方法创建1个Post，返回字符串
• updatePost 方法更新第1个Post，返回字符串
• deletePost 方法删除第1个Post，返回字符串

AppDelegate

在 AppDelegate.swift 中添加 RxSwift 的引用，然后在 AppDelegate 类中添加 DisposeBag 类型的实例。

import RxSwift

class AppDelegate {
// ...
let disposeBag = DisposeBag()
// ...
}

在 AppDelegate 类的 applicationDidFinishLaunching 方法中添加以下代码

Post.getPostAsString().do(onNext: { print($0) }).subscribe().disposed(by: disposeBag)
Post.getPostAsJson().do(onNext: { print($0.description) }).subscribe().disposed(by: disposeBag)
Post.getPosts(n: 2).do(onNext: { print($0.description) }).subscribe().disposed(by: disposeBag)
Post.createPost().do(onNext: { print($0) }).subscribe().disposed(by: disposeBag)
Post.updatePost().do(onNext: { print($0) }).subscribe().disposed(by: disposeBag)
Post.deletePost().do(onNext: { print($0) }).subscribe().disposed(by: disposeBag)

输出结果

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
  "body": "quia et suscipit
suscipit recusandae consequuntur expedita et cum
reprehenderit molestiae ut ut quas totam
nostrum rerum est autem sunt rem eveniet architecto"
}
Post {userId = 1, id = 1, title = "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", body = "quia et suscipit
suscipit recusandae consequuntur expedita et cum
reprehenderit molestiae ut ut quas totam
nostrum rerum est autem sunt rem eveniet architecto"}
Post {userId = 1, id = 2, title = "qui est esse", body = "est rerum tempore vitae
sequi sint nihil reprehenderit dolor beatae ea dolores neque
fugiat blanditiis voluptate porro vel nihil molestiae ut reiciendis
qui aperiam non debitis possimus qui neque nisi nulla"}
Post {userId = 1, id = 1, title = "sunt aut facere repellat provident occaecati excepturi optio reprehenderit", body = "quia et suscipit
suscipit recusandae consequuntur expedita et cum
reprehenderit molestiae ut ut quas totam
nostrum rerum est autem sunt rem eveniet architecto"}
{}
{
  "{"body":"test body","id":0,"title":"test title","userId":101}": "",
  "id": 101
}
{
  "id": 1
}