问题描述
我想从服务器获取数据并更新数据库,然后再向用户显示接收到的数据。为了这个目标,我在视图模型中有一个方法(getData()
),该方法返回我调用的Single
并首先在该方法的视图控制器(myVC.getData.subscribe({single in ...})
)中预订此方法。并订阅了(#1)(getUnread()->Single
)方法,但我无法获得单个事件,我无法理解为什么无法在回调(#4)中获得事件(#3)>
之后,我想通过调用(#2)(save([Moddel])-> single)保存数据
//I removed some part of this code it was to big
//This method is View Model
func getData() -> Single<[Model]> {
return Single<[Model]>.create {[weak self] single in
//#1
self!.restRepo.getUnread().subscribe({ [weak self] event in
//#4
switch event {
case .success(let response):
let models = response
//#2
self!.dbRepo.save(issues!).subscribe({ event in
switch event {
case .success(let response):
let models = response
single(.success(models))
case .error(let error):
single(.error(error))
}
}).disposed(by: self!.disposeBag)
case .error(let error):
single(.error(error))
}
}).disposed(by: self!.disposeBag)
return disposables.create()
}
}
。
//I removed some part of this code it was to big
//This method is in RestRepo class
func getUnread() -> Single<[Model]> {
return Single<[Model]>.create { single in
let urlComponent = ApiHelper.instance.dolphinURLComponents(for: ApiHelper.ISSUES_PATH)
var urlRequest = URLRequest(url: urlComponent.url!)
ApiHelper.instance.alamofire.request(urlRequest).intercept().responseJSON { response in
debugPrint(response)
let statusCode = response.response?.statusCode
switch statusCode {
case 200:
do {
let models = try JSONDecoder().decode([Model].self,from: response.data!)
//#3
single(.success(models))
}catch{
print(error)
}
case 304:
debugPrint(response)
default:
single(.error(IssueResponseStatusCodeError(code: statusCode ?? 0)))
}
}
return disposables.create()
}
解决方法
首先,您需要改变想法。 您在该应用中不执行任何操作。充其量,您要布置可观察的链条(除了水管“做”某事以外,它们什么都不做。)然后启动应用程序,让“水”流过。
考虑到这一点,让我们检查一下您的问题:
我想从服务器获取数据...
不是“您”想要获取数据。该请求是由于用户的某些操作(可能是点击按钮)或其他副作用而做出的。那是什么动作?这需要在代码中表达。对于以下内容,我将假定它是一个按钮点击。那意味着你应该有:
class Example: UIViewController {
var button: UIButton!
var restRepo: RestRepo!
override func viewDidLoad() {
super.viewDidLoad()
let serverResponse = button.rx.tap
.flatMapLatest { [restRepo] in
restRepo!.getUnread()
.map { Result<[Model],Error>.success($0) }
.catchError { .just(Result<[Model],Error>.failure($0)) }
}
.share(replay: 1)
}
}
protocol RestRepo {
func getUnread() -> Observable<[Model]>
}
struct ProductionRestRepo: RestRepo {
func getUnread() -> Observable<[Model]> {
let urlComponent = ApiHelper.instance.dolphinURLComponents(for: ApiHelper.ISSUES_PATH)
let urlRequest = URLRequest(url: urlComponent.url!)
return URLSession.shared.rx.data(request: urlRequest)
.map { try JSONDecoder().decode([Model].self,from: $0) }
}
}
class ApiHelper {
static let ISSUES_PATH = ""
static let instance = ApiHelper()
func dolphinURLComponents(for: String) -> URLComponents { fatalError() }
}
struct Model: Decodable { }
这里要注意的是getUnread()
是由button.rx.tap
引起的影响。以上建立了因果链。
您的问题继续说“您”想要:
...更新我的数据库...
这里,原因是网络请求,结果是数据库保存,因此我们只需要将其添加到viewDidLoad中(请注意,下面的代码使用RxEnumKit。):
let dbResponse = serverResponse
.capture(case: Result.success)
.flatMapLatest { [dbRepo] models in
dbRepo!.save(models)
.map { Result<Void,Error>.success(()) }
.catchError { .just(Result<Void,Error>.failure($0)) }
}
您的问题还表明“您”想要:
...向用户显示接收到的数据。
请注意,向用户显示接收到的数据与数据库保存无关。它们是两个可以并行完成的独立操作。
向用户显示接收到的数据时,将serverResponse作为原因,将其显示为结果。
serverResponse
.capture(case: Result.success)
.subscribe(onNext: { models in
print("display the data to the user.",models)
})
.disposed(by: disposeBag)
最后,您没有提到它,但是您还必须处理错误:
因此也将其添加到viewDidLoad中:
Observable.merge(serverResponse.capture(case: Result.failure),dbResponse.capture(case: Result.failure))
.subscribe(onNext: { error in
print("an error occured:",error)
})
.disposed(by: disposeBag)
下面的代码作为单个块包含以上所有内容。这样编译就可以了...
import UIKit
import RxSwift
import RxCocoa
import EnumKit
import RxEnumKit
extension Result: CaseAccessible { }
class Example: UIViewController {
var button: UIButton!
var restRepo: RestRepo!
var dbRepo: DBRepo!
let disposeBag = DisposeBag()
override func viewDidLoad() {
super.viewDidLoad()
let serverResponse = button.rx.tap
.flatMapLatest { [restRepo] in
restRepo!.getUnread()
.map { Result<[Model],Error>.failure($0)) }
}
.share(replay: 1)
let dbResponse = serverResponse
.capture(case: Result.success)
.flatMapLatest { [dbRepo] models in
dbRepo!.save(models)
.map { Result<Void,Error>.success(()) }
.catchError { .just(Result<Void,Error>.failure($0)) }
}
serverResponse
.capture(case: Result.success)
.subscribe(onNext: { models in
print("display the data to the user.",models)
})
.disposed(by: disposeBag)
Observable.merge(serverResponse.capture(case: Result.failure),dbResponse.capture(case: Result.failure))
.subscribe(onNext: { error in
print("an error occured:",error)
})
.disposed(by: disposeBag)
}
}
protocol RestRepo {
func getUnread() -> Observable<[Model]>
}
protocol DBRepo {
func save(_ models: [Model]) -> Observable<Void>
}
struct ProductionRestRepo: RestRepo {
func getUnread() -> Observable<[Model]> {
let urlComponent = ApiHelper.instance.dolphinURLComponents(for: ApiHelper.ISSUES_PATH)
let urlRequest = URLRequest(url: urlComponent.url!)
return URLSession.shared.rx.data(request: urlRequest)
.map { try JSONDecoder().decode([Model].self,from: $0) }
}
}
class ApiHelper {
static let ISSUES_PATH = ""
static let instance = ApiHelper()
func dolphinURLComponents(for: String) -> URLComponents { fatalError() }
}
struct Model: Decodable { }
希望所有这些对您有所帮助,或者至少会引发更多问题。