![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
return rxResponse(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}
APIClient.responseObservable(request: req)
.subscribe(onNext: { data in
// handle data
})](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-33-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
return rxResponse(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}
APIClient.responseObservable(request: req)
.subscribe(onNext: { data in
// handle data
})](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-34-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
return rxResponse(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}
APIClient.responseObservable(request: req)
.subscribe(onNext: { data in
// handle data
})](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-35-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
return rxResponse(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}
APIClient.responseObservable(request: req)
.subscribe(onNext: { data in
// handle data
})](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-36-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
return rxResponse(request)
.flatMap { handleResponse }
.retry(3)
.retryWhen { handleErrors }
}
}
APIClient.responseObservable(request: req)
.subscribe(onNext: { data in
// handle data
})](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-37-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
return rxResponse(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}
APIClient.responseObservable(request: req)
.subscribe(onNext: { data in
// handle data
})](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-38-320.jpg)
![private static func handleResponse(
data: Data?, response: URLResponse?
) throws -> Observable<[String: Any]> {
guard let httpResponse = response as? HTTPURLResponse else {
throw APIError.invalidResponse(response)
}
guard 200..<300 ~= httpResponse.statusCode else {
throw APIError.badStatusCode(httpResponse)
}
guard let responseData = data else {
throw APIError.badData(data, httpResponse)
}
if let json = try JSONSerialization
.jsonObject(with: responseData, options: []) as? [String: Any] {
return Observable.just(json)
} else {
throw APIError.jsonParsingError
}
}
class APIClient {
let apiClientDisposeBag = DisposeBag()
static func responseObservable(
request: URLRequest
) -> Observable<[String: Any]> {
return customRequest(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-39-320.jpg)
![private static func handleResponse(
data: Data?, response: URLResponse?
) throws -> Observable<[String: Any]> {
guard let httpResponse = response as? HTTPURLResponse else {
throw APIError.invalidResponse(response)
}
guard 200..<300 ~= httpResponse.statusCode else {
throw APIError.badStatusCode(httpResponse)
}
guard let responseData = data else {
throw APIError.badData(data, httpResponse)
}
if let json = try JSONSerialization
.jsonObject(with: responseData, options: []) as? [String: Any] {
return Observable.just(json)
} else {
throw APIError.jsonParsingError
}
}
class APIClient {
let apiClientDisposeBag = DisposeBag()
static func responseObservable(
request: URLRequest
) -> Observable<[String: Any]> {
return customRequest(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-40-320.jpg)
![private static func handleErrors(errors: Observable<Error>)
-> Observable<Void> {
return errors.enumerated()
.flatMap { (i, error) -> Observable<Void> in
// handle max number of retries based on `i`
guard i < 3 else {
return Observable.error(error) // propagate error
}
switch error {
case .expiredToken:
self.refreshToken()
return Observable.just(()) // <- forces retry
default:
return Observable.just(()) // <- forces retry
}
}
}
class APIClient {
let apiClientDisposeBag = DisposeBag()
static func responseObservable(
request: URLRequest
) -> Observable<[String: Any]> {
return customRequest(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-41-320.jpg)
![private static func handleErrors(errors: Observable<Error>)
-> Observable<Void> {
return errors.enumerated()
.flatMap { (i, error) -> Observable<Void> in
// handle max number of retries based on `i`
guard i < 3 else {
return Observable.error(error) // propagate error
}
switch error {
case .expiredToken:
self.refreshToken()
return Observable.just(()) // <- forces retry
default:
return Observable.just(()) // <- forces retry
}
}
}
class APIClient {
let apiClientDisposeBag = DisposeBag()
static func responseObservable(
request: URLRequest
) -> Observable<[String: Any]> {
return customRequest(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-42-320.jpg)
![private static func handleErrors(errors: Observable<Error>)
-> Observable<Void> {
return errors.enumerated()
.flatMap { (i, error) -> Observable<Void> in
// handle max number of retries based on `i`
guard i < 3 else {
return Observable.error(error) // propagate error
}
switch error {
case .expiredToken:
self.refreshToken()
return Observable.just(()) // <- forces retry
default:
return Observable.just(()) // <- forces retry
}
}
}
class APIClient {
let apiClientDisposeBag = DisposeBag()
static func responseObservable(
request: URLRequest
) -> Observable<[String: Any]> {
return customRequest(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-43-320.jpg)
![private static func handleErrors(errors: Observable<Error>)
-> Observable<Void> {
return errors.enumerated()
.flatMap { (i, error) -> Observable<Void> in
// handle max number of retries based on `i`
guard i < 3 else {
return Observable.error(error) // propagate error
}
switch error {
case .expiredToken:
self.refreshToken()
return Observable.just(()) // <- forces retry
default:
return Observable.just(()) // <- forces retry
}
}
}
class APIClient {
let apiClientDisposeBag = DisposeBag()
static func responseObservable(
request: URLRequest
) -> Observable<[String: Any]> {
return customRequest(request)
.flatMap { handleResponse }
// .retry(3)
.retryWhen { handleErrors }
}
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-44-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
...
}
static func response(request: URLRequest, completion: @escaping ([String: Any])->Void) {
responseObservable(request: request)
.subscribe(onNext: { data in
completion(data)
})
.disposed(by: apiClientDisposeBag)
}
}
APIClient.response(request: req) { json in
// do stuff with json
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-45-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
...
}
static func response(request: URLRequest, completion: @escaping ([String: Any])->Void) {
responseObservable(request: request)
.subscribe(onNext: { data in
completion(data)
})
.disposed(by: apiClientDisposeBag)
}
}
APIClient.response(request: req) { json in
// do stuff with json
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-46-320.jpg)
![class APIClient {
static func responseObservable(request: URLRequest)
-> Observable<[String: Any]> {
...
}
static func response(request: URLRequest, completion: @escaping ([String: Any])->Void) {
responseObservable(request: request)
.subscribe(onNext: { data in
completion(data)
})
.disposed(by: apiClientDisposeBag)
}
}
APIClient.response(request: req) { json in
// do stuff with json
}](https://image.slidesharecdn.com/rx-180103043050/85/Intro-to-Reactive-Programming-with-Swift-47-320.jpg)
Intro to Reactive Programming with Swift
- 1. Introduction to Reactive Programming with RxSwift Xinran Wang Software Engineer Digital Home, Comcast NBCUniversal
- 2. What is Reactive Programming? Programming with asynchronous data streams Treat events as sequences (streams) of data
- 3. Improve API client retries and error handling Simplify app auth management
- 4. someAsyncFunction { anotherAsyncFunction1 { anotherAsyncFunction2 { anotherAsyncFunction3 { anotherAsyncFunction4 { // Thank God this has no error handling 😰 } } } } }
- 5. asyncObservable() .flatMap { _ in return asyncObservable2() } .flatMap { _ in return asyncObservable3() } .flatMap { _ in return asyncObservable4() } .subscribe(onNext: { data in // handle last result }, onError{ error in // handle errors })
- 6. Main Terminology (the boring stuff)
- 7. Streams of data (think Swift sequences + async) Observable
- 8. Event An element/value of the data stream onNext: onError: onComplete:
- 9. Observer/Subscriber Subscribes to the … Observable Handles Events (the data stream elements) Stream starts on“subscription”
- 10. Disposable Disconnects the data stream Ends Event ingestion Handles cleanup of resources
- 11. Main Terminology - Observable - Event - Subscriber - Disposable Icons made by https://www.flaticon.com/authors/smashicons from www.flaticon.com
- 12. Main Terminology - Observable - Event - Subscriber - Disposable
- 13. Main Terminology - Observable - Event - Subscriber - Disposable
- 14. Main Terminology - Observable - Event - Subscriber - Disposable
- 15. Ok, now the fun stuff: what do I do with these data streams?
- 16. Rx Operators! (the fun stuff) // Creating: create, from, just … // Transforming map, flatMap, buffer … // Filtering filter, first, skip, debounce … // Combining merge, zip, combineLatest … // Error Handling catch, retry // Utility subscribe, delay, do … // Conditional/Boolean contains, all, skipUntil … // Mathematical and Aggregation count, max, min, reduce …
- 17. Creating! // Creating: create, from, just … // Transforming map, flatMap, buffer … // Filtering filter, first, skip, debounce … // Combining merge, zip, combineLatest … // Error Handling catch, retry // Utility subscribe, delay, do … // Conditional/Boolean contains, all, skipUntil … // Mathematical and Aggregation count, max, min, reduce …
- 18. Observable.create { observer in asyncFunction(completion: { // create the event for each piece of data // observer.onNext() // observer.onError() // observer.onComplete() }) return Disposables.create() }
- 19. func makeSushi(completion: @escaping (Sushi?, Error?)->Void) func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } }
- 20. func makeSushi(completion: @escaping (Sushi?, Error?)->Void) func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } }
- 21. func makeSushi(completion: @escaping (Sushi?, Error?)->Void) func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } }
- 22. func makeSushi(completion: @escaping (Sushi?, Error?)->Void) func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } }
- 23. func makeSushi(completion: @escaping (Sushi?, Error?)->Void) func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } }
- 24. func makeSushi(completion: @escaping (Sushi?, Error?)->Void) func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } }
- 25. func makeSushi(completion: @escaping (Sushi?, Error?)->Void) func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } }
- 26. func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } } makeSushiObservable() // observable stream STARTS on subscription // so makeSushi actually first gets called here .subscribe(onNext: { sushi in // eat the sushi! }, onError: { error in // complain to the waiter }) .disposed(by: disposeBag)
- 27. func makeSushiObservable() -> Observable<Sushi?> { return Observable.create { observer in self.makeSushi { (sushi, error) in if let error = error { observer.onError(error) } observer.onNext(sushi) observer.onCompleted() } return Disposables.create() } } makeSushiObservable() // observable stream STARTS on subscription // so makeSushi actually first gets called here .subscribe(onNext: { sushi in // eat the sushi! }, onError: { error in // complain to the waiter }) .disposed(by: disposeBag)
- 28. More Operators! // Creating: create, from, just … // Transforming map, flatMap, buffer … // Filtering filter, first, skip, debounce … // Combining merge, zip, combineLatest … // Error Handling catch, retry // Utility subscribe, delay, do … // Conditional/Boolean contains, all, skipUntil … // Mathematical and Aggregation count, max, min, reduce …
- 29. let sushi = Observable.zip(makeRice(), sliceFish(tuna)) { (rice, tuna) -> Sushi in return Sushi(rice, tuna) } sushi.filter { sushi in return !sushi.isVegetarian() } .map { (sushi: Sushi) -> Sushi in return addSoySauce(sushi) } .map { addWasabi }
- 30. let sushi = Observable.zip(makeRice(), sliceFish(tuna)) { (rice, tuna) -> Sushi in return Sushi(rice, tuna) } sushi.filter { sushi in return !sushi.isVegetarian() } .map { (sushi: Sushi) -> Sushi in return addSoySauce(sushi) } .map { addWasabi }
- 31. Cool … Why and how would I actually use this for building my iOS app?
- 32. Networking Unified Error Handling & Better Retries
- 33. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { return rxResponse(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } } APIClient.responseObservable(request: req) .subscribe(onNext: { data in // handle data })
- 34. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { return rxResponse(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } } APIClient.responseObservable(request: req) .subscribe(onNext: { data in // handle data })
- 35. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { return rxResponse(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } } APIClient.responseObservable(request: req) .subscribe(onNext: { data in // handle data })
- 36. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { return rxResponse(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } } APIClient.responseObservable(request: req) .subscribe(onNext: { data in // handle data })
- 37. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { return rxResponse(request) .flatMap { handleResponse } .retry(3) .retryWhen { handleErrors } } } APIClient.responseObservable(request: req) .subscribe(onNext: { data in // handle data })
- 38. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { return rxResponse(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } } APIClient.responseObservable(request: req) .subscribe(onNext: { data in // handle data })
- 39. private static func handleResponse( data: Data?, response: URLResponse? ) throws -> Observable<[String: Any]> { guard let httpResponse = response as? HTTPURLResponse else { throw APIError.invalidResponse(response) } guard 200..<300 ~= httpResponse.statusCode else { throw APIError.badStatusCode(httpResponse) } guard let responseData = data else { throw APIError.badData(data, httpResponse) } if let json = try JSONSerialization .jsonObject(with: responseData, options: []) as? [String: Any] { return Observable.just(json) } else { throw APIError.jsonParsingError } } class APIClient { let apiClientDisposeBag = DisposeBag() static func responseObservable( request: URLRequest ) -> Observable<[String: Any]> { return customRequest(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } }
- 40. private static func handleResponse( data: Data?, response: URLResponse? ) throws -> Observable<[String: Any]> { guard let httpResponse = response as? HTTPURLResponse else { throw APIError.invalidResponse(response) } guard 200..<300 ~= httpResponse.statusCode else { throw APIError.badStatusCode(httpResponse) } guard let responseData = data else { throw APIError.badData(data, httpResponse) } if let json = try JSONSerialization .jsonObject(with: responseData, options: []) as? [String: Any] { return Observable.just(json) } else { throw APIError.jsonParsingError } } class APIClient { let apiClientDisposeBag = DisposeBag() static func responseObservable( request: URLRequest ) -> Observable<[String: Any]> { return customRequest(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } }
- 41. private static func handleErrors(errors: Observable<Error>) -> Observable<Void> { return errors.enumerated() .flatMap { (i, error) -> Observable<Void> in // handle max number of retries based on `i` guard i < 3 else { return Observable.error(error) // propagate error } switch error { case .expiredToken: self.refreshToken() return Observable.just(()) // <- forces retry default: return Observable.just(()) // <- forces retry } } } class APIClient { let apiClientDisposeBag = DisposeBag() static func responseObservable( request: URLRequest ) -> Observable<[String: Any]> { return customRequest(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } }
- 42. private static func handleErrors(errors: Observable<Error>) -> Observable<Void> { return errors.enumerated() .flatMap { (i, error) -> Observable<Void> in // handle max number of retries based on `i` guard i < 3 else { return Observable.error(error) // propagate error } switch error { case .expiredToken: self.refreshToken() return Observable.just(()) // <- forces retry default: return Observable.just(()) // <- forces retry } } } class APIClient { let apiClientDisposeBag = DisposeBag() static func responseObservable( request: URLRequest ) -> Observable<[String: Any]> { return customRequest(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } }
- 43. private static func handleErrors(errors: Observable<Error>) -> Observable<Void> { return errors.enumerated() .flatMap { (i, error) -> Observable<Void> in // handle max number of retries based on `i` guard i < 3 else { return Observable.error(error) // propagate error } switch error { case .expiredToken: self.refreshToken() return Observable.just(()) // <- forces retry default: return Observable.just(()) // <- forces retry } } } class APIClient { let apiClientDisposeBag = DisposeBag() static func responseObservable( request: URLRequest ) -> Observable<[String: Any]> { return customRequest(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } }
- 44. private static func handleErrors(errors: Observable<Error>) -> Observable<Void> { return errors.enumerated() .flatMap { (i, error) -> Observable<Void> in // handle max number of retries based on `i` guard i < 3 else { return Observable.error(error) // propagate error } switch error { case .expiredToken: self.refreshToken() return Observable.just(()) // <- forces retry default: return Observable.just(()) // <- forces retry } } } class APIClient { let apiClientDisposeBag = DisposeBag() static func responseObservable( request: URLRequest ) -> Observable<[String: Any]> { return customRequest(request) .flatMap { handleResponse } // .retry(3) .retryWhen { handleErrors } } }
- 45. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { ... } static func response(request: URLRequest, completion: @escaping ([String: Any])->Void) { responseObservable(request: request) .subscribe(onNext: { data in completion(data) }) .disposed(by: apiClientDisposeBag) } } APIClient.response(request: req) { json in // do stuff with json }
- 46. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { ... } static func response(request: URLRequest, completion: @escaping ([String: Any])->Void) { responseObservable(request: request) .subscribe(onNext: { data in completion(data) }) .disposed(by: apiClientDisposeBag) } } APIClient.response(request: req) { json in // do stuff with json }
- 47. class APIClient { static func responseObservable(request: URLRequest) -> Observable<[String: Any]> { ... } static func response(request: URLRequest, completion: @escaping ([String: Any])->Void) { responseObservable(request: request) .subscribe(onNext: { data in completion(data) }) .disposed(by: apiClientDisposeBag) } } APIClient.response(request: req) { json in // do stuff with json }
- 48. Final Thoughts
- 49. Final Thoughts 1. 👎 Avoid nesting subscriptions
- 50. APIClient.fetchMovie(id).subscribe(onNext: { movie in APIClient.fetchMovieDetails(movie).subscribe(onNext: { details in ... }) .addDisposableTo(disposeBag) }) .addDisposableTo(disposeBag) APIClient.fetchMovie(id) .flatMap { id in return APIClient.fetchMovieDetails(movie) } .subscribe(onNext: { details in ... }) .addDisposableTo(disposeBag)
- 51. APIClient.fetchMovie(id).subscribe(onNext: { movie in APIClient.fetchMovieDetails(movie).subscribe(onNext: { details in ... }) .addDisposableTo(disposeBag) }) .addDisposableTo(disposeBag) APIClient.fetchMovie(id) .flatMap { id in return APIClient.fetchMovieDetails(movie) } .subscribe(onNext: { details in ... }) .addDisposableTo(disposeBag)
- 52. Final Thoughts 2. Makes networking cleaner
- 53. Final Thoughts 3. Rx forces your code to be more functional
- 54. Final Thoughts 4. Can go from callbacks to observable The whole project does not need to be observable
- 55. Useful Resources General: - http://reactivex.io/documentation/observable.html - http://rxmarbles.com/ RxSwift-specific: - https://github.com/ReactiveX/RxSwift - https://egghead.io/courses/introduction-to-reactive-programming - https://www.raywenderlich.com/138547/getting-started-with-rxswift-and-rxcocoa - https://www.raywenderlich.com/158026/introducing-rxswift-reactive-programming-swift