Declarative Networking with Combine –– iOS Conf SG 2020

Transcript

1. #DroidConBos @ragdroid
   Declarative Networking
   with Combine
   Ritesh Gupta
   iOS Conf SG 2020
   

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2. @_riteshhh
   fueled.com/ritesh
   twitter.com/@_riteshhh
   riteshhh.com
   github.com/riteshhgupta
   Ritesh Gupta
   

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3. @_riteshhh
   Combine
   It’s a new reactive framework by Apple
   which provides a declarative Swift API for
   processing values over time.
   

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4. @_riteshhh
   Pillars of Combine
   Publisher
   Just
   Fail
   Future
   DataTaskPublisher
   Map
   FlatMap
   Filter
   Catch
   Sink
   Assign
   AnySubscriber
   [Operators] Subscriber
   

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5. @_riteshhh
   Networking
   • URLSession
   • URLSessionDataTask
   • func dataTask(URL) -> URLSessionDataTask
   (without Combine)
   

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6. @_riteshhh
   Networking
   (with Combine)
   • URLSession
   • URLSession.DataTaskPublisher
   • func dataTaskPublisher(URL) -> DataTaskPublisher
   

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7. @_riteshhh
   DataTaskPublisher
   typealias DataTaskResult = (Data, URLResponse)
   public struct DataTaskPublisher : Publisher {
   /// The kind of values published by this publisher.
   public typealias Output = DataTaskResult
   /// The kind of errors this publisher might publish.
   public typealias Failure = URLError
   }
   

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8. @_riteshhh
   DataTaskPublisher
   let url = URL(string: "http://api.openweathermap.org/data/2.5")!
   let session = URLSession.shared
   session
   .dataTaskPublisher(for: url)
   .sink(
   receiveCompletion: { print("Completion/Failure: \($0)") },
   receiveValue: { print("Value: \($0)") }
   )
   

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9. @_riteshhh
   DataTaskPublisher
   let url = URL(string: "http://api.openweathermap.org/data/2.5")!
   let session = URLSession.shared
   session
   .dataTaskPublisher(for: url)
   .sink(
   receiveCompletion: { print("Completion/Failure: \($0)") },
   receiveValue: { print("Value: \($0)") }
   )
   

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10. @_riteshhh
    DataTaskPublisher
    let url = URL(string: "http://api.openweathermap.org/data/2.5")!
    let session = URLSession.shared
    session
    .dataTaskPublisher(for: url)
    .sink(
    receiveCompletion: { print("Completion/Failure: \($0)") },
    receiveValue: { print("Value: \($0)") }
    )
    •Gateway timeout error
    •No internet error
    

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11. @_riteshhh
    DataTaskPublisher
    let url = URL(string: "http://api.openweathermap.org/data/2.5")!
    let session = URLSession.shared
    session
    .dataTaskPublisher(for: url)
    .sink(
    receiveCompletion: { print("Completion/Failure: \($0)") },
    receiveValue: { print("Value: \($0)") }
    )
    •401: Invalid API Key
    •404: Not found
    

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12. @_riteshhh
    Validation
    • move response into correct stream
    (i.e. 4xx response into failure stream
    and 2xx into output/value stream)
    

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13. @_riteshhh
    Validation
    func validateResponse()
    

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14. @_riteshhh
    Validation
    func validateResponse() -> ValidatedPublisher
    enum ValidationError: Error {
    case error(Error)
    case jsonError(Data)
    }
    typealias ValidatedPublisher = AnyPublisher
    typealias DataTaskResult = (Data, URLResponse)
    

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15. @_riteshhh
    Validation
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher
    typealias IsValidCallback = (DataTaskResult) -> Bool
    typealias ValidatedPublisher = AnyPublisher
    typealias DataTaskResult = (Data, URLResponse)
    

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16. @_riteshhh
    Validation
    extension Publisher where Output == DataTaskResult {
    func validateResponse(isValid: IsValidCallBack)
    -> ValidatedPublisher
    }
    

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17. @_riteshhh
    Validation
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    }
    

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18. @_riteshhh
    Validation
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    }
    

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19. @_riteshhh
    Validation
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in }
    }
    

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20. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output/Success stream
    } else {
    // return the value in the Failure stream
    }
    }
    }
    

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21. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output/Success stream
    } else {
    // return the value in the Failure stream
    }
    }
    }
    

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22. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output stream
    return Just(result)
    .setFailureType(to: ValidationError.self)
    .eraseToAnyPublisher()
    } else {
    // return the value in the Failure stream
    }
    }
    }
    

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23. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output stream
    return Just(result)
    .setFailureType(to: ValidationError.self)
    .eraseToAnyPublisher()
    } else {
    // return the value in the Failure stream
    }
    }
    }
    

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24. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output stream
    return Just(result)
    .setFailureType(to: ValidationError.self)
    .eraseToAnyPublisher()
    } else {
    // return the value in the Failure stream
    return Fail(
    outputType: DataTaskResult.self,
    failure: ValidationError.jsonError(result.data)
    ).eraseToAnyPublisher()
    }
    }
    }
    

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25. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output stream
    return Just(result)
    .setFailureType(to: ValidationError.self)
    .eraseToAnyPublisher()
    } else {
    // return the value in the Failure stream
    return Fail(
    outputType: DataTaskResult.self,
    failure: ValidationError.jsonError(result.data)
    ).eraseToAnyPublisher()
    }
    }
    }
    

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26. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output stream
    return Just(result)
    .setFailureType(to: ValidationError.self)
    .eraseToAnyPublisher()
    } else {
    // return the value in the Failure stream
    return Fail(
    outputType: DataTaskResult.self,
    failure: ValidationError.jsonError(result.data)
    ).eraseToAnyPublisher()
    }
    }
    }
    

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27. @_riteshhh
    func validateResponse(isValid: IsValidCallback)
    -> ValidatedPublisher {
    return self
    .mapError { ValidationError.error($0) }
    .flatMap { (result) -> ValidatedPublisher in
    if isValid(result) {
    // return the value in the Output stream
    return Just(result)
    .setFailureType(to: ValidationError.self)
    .eraseToAnyPublisher()
    } else {
    // return the value in the Failure stream
    return Fail(
    outputType: Output.self,
    failure: ValidationError.jsonError(result.data)
    ).eraseToAnyPublisher()
    }
    }.eraseToAnyPublisher()
    }
    

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28. @_riteshhh
    func validateStatusCode(_ isValid: (Int) -> Bool) -> ValidatedPublisher {
    return validateResponse { (data, response) in
    let statusCode = (response as? HTTPURLResponse)?.statusCode ?? -1
    return isValid(statusCode)
    }
    }
    func validateResponse(isValid: (DataTaskResult) -> Bool)
    -> ValidatedPublisher { ... }
    Validation
    

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29. @_riteshhh
    let url = URL(string: "http://api.openweathermap.org/data/2.5")!
    let session = URLSession.shared
    session
    .dataTaskPublisher(for: url)
    .sink(
    receiveCompletion: { print("Completion/Failure: \($0)") },
    receiveValue: { print("Value: \($0)") }
    )
    Declarative Networking
    

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30. @_riteshhh
    let url = URL(string: "http://api.openweathermap.org/data/2.5")!
    let session = URLSession.shared
    session
    .dataTaskPublisher(for: url)
    .validateStatusCode { (200..<300).contains($0) }
    .sink(
    receiveCompletion: { print("Completion/Failure: \($0)") },
    receiveValue: { print("Value: \($0)") }
    )
    Declarative Networking
    

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31. @_riteshhh
    let url = URL(string: "http://api.openweathermap.org/data/2.5")!
    let session = URLSession.shared
    session
    .dataTaskPublisher(for: url)
    .validateStatusCode { (200..<300).contains($0) }
    .validateResponse { !$0.data.isEmpty }
    .sink(
    receiveCompletion: { print("Completion/Failure: \($0)") },
    receiveValue: { print("Value: \($0)") }
    )
    Declarative Networking
    

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32. @_riteshhh
    let url = URL(string: "http://api.openweathermap.org/data/2.5")!
    let session = URLSession.shared
    session
    .dataTaskPublisher(for: url)
    .validateStatusCode { (200..<300).contains($0) }
    .validateResponse { !$0.data.isEmpty }
    .mapErrorJson(to: ApiErrorResponse.self, decoder: decoder)
    .sink(
    receiveCompletion: { print("Completion/Failure: \($0)") },
    receiveValue: { print("Value: \($0)") }
    )
    Declarative Networking
    

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33. @_riteshhh
    let url = URL(string: "http://api.openweathermap.org/data/2.5")!
    let session = URLSession.shared
    session
    .dataTaskPublisher(for: url)
    .validateStatusCode { (200..<300).contains($0) }
    .validateResponse { !$0.data.isEmpty }
    .mapErrorJson(to: ApiErrorResponse.self, decoder: decoder)
    .mapValueJson(to: ApiValueResponse.self, decoder: decoder)
    .sink(
    receiveCompletion: { print("Completion/Failure: \($0)") },
    receiveValue: { print("Value: \($0)") }
    )
    Declarative Networking
    

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34. @_riteshhh
    Further reading
    • Declarative Networking with Combine ––
    riteshhh.com
    • Awesome Combine –– Github
    

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35. @_riteshhh
    Thank you!
    
    

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