Alamofire 5.0 Migration Guide.md

Alamofire 5.0 Migration Guide

Alamofire 5.0 is the latest major release of Alamofire, an HTTP networking library for iOS, tvOS, macOS and watchOS written in Swift. As a major release, following Semantic Versioning conventions, 5.0 introduces API-breaking changes.

This guide is provided in order to ease the transition of existing applications using Alamofire 4.x to the latest APIs, as well as explain the design and structure of new and updated functionality. Due to the extensive nature of the changes in Alamofire 5, this guide does not provide a complete overview of all changes. Instead, the largest changes are summarized and users encouraged to read Alamofire’s extensive API, Usage, and Advanced Usage documentation.

Benefits of Upgrading

• Rewritten Core: Alamofire’s core architecture has been rewritten to follow a variety of best practices.
  • DispatchQueue usage has been updated to follow Apple’s recommended best practices. This means Alamofire will scale much better when many requests are in flight at the same time cannot lead to queue exhaustion like previous versions could. This should improve overall performance and lower the impact of Alamofire on the app and system.
  • Areas of responsibility have been clarified among internal APIs, making it easier to implement certain features, like the new EventMonitor protocol and per-request SSL failure errors, among many others.
  • It was written with the benefit of the various sanitizers, especially the thread sanitizer, from the very beginning, so there will be far fewer threading and other runtime issues than seen in previous versions.
• Decodable Responses: responseDecodable and the DecodableResponseSerializer now provide built-in support for parsing Decodable types from network responses using any DataDecoder type.
• Encodable Parameters: Alamofire now supports and prefers Encodable types as parameters using the ParameterEncoder protocol, allowing fully type-safe representation of request parameters.
• URLEncodedFormEncoder: In addition to supporting Encodable parameters in general, Alamofire now includes the URLEncodedFormEncoder, an Encoder for URL form encoding.
• EventMonitor Protocol: EventMonitors allow access to Alamofire’s internal events, making it far easier to observe specific actions through a request’s lifetime. This makes logging requests very easy.
• Async RequestAdapters: The RequestAdapter protocol now operates asynchronously, making it possible to add async resources to requests.
• Per-Request RequestInterceptors: RequestInterceptors can now be added to individual Requests, allowing fine-grained control for the first time.
• CachedResponseHandler and RedirectHandler Protocols: Easy access and control over response caching and redirect behaviors, on both a Session and Request basis.
• HTTPHeaders Type: Type safe access to common HTTP headers, with extensions to URLRequest, HTTPURLResponse, and URLSessionConfiguration to allow setting the headers of those types using Alamofire’s new type.
• RetryPolicy: A RequestRetrier with automatic support for retrying requests which failed due to a network or other system error, with customizable exponential backoff, retry limits, and other parameters.

Breaking API Changes

Most APIs have changed in Alamofire 5, so this list is not complete. While most top level request APIs remain the same, nearly every other type has changed in some way. For up to date examples, see our Usage and Advanced Usage documentation.

• SessionManager has been renamed to Session and its APIs have completely changed.
• Background URLSessionConfigurations are no longer supported and attempting to use one will result in a fatal runtime error. Alamofire was never designed to work in the background and its closure-based APIs cannot survive a background transition, leading to ongoing issues around background behavior. Explicit background support will be added through dedicated APIs at some point in the future.
• SessionDelegate has been rebuilt and it’s public API completely changed. The various closure overrides have been removed, with most now able to be replaced with specific Alamofire features. If there is a need for control over something the closures used to provide, feel free to open a feature request.
• TaskDelegate and the various *TaskDelegate classes have been removed. All URLSession*Delegate handling is now performed by SessionDelegate.
• Result has been removed. Alamofire now uses Swift’s Result type.
• Global Alamofire namespace usage, which was never really necessary, has been removed and replaced with a single AF reference to Session.default.
• ServerTrustPolicyManager has been renamed ServerTrustManager and now requires every evaluated request to match one of the provided hosts. This can be disabled by initializing an instance with allHostsMustBeEvaluated: false.
• ServerTrustPolicy has be separated into a protocol, ServerTrustEvaluating, and several conforming types. Each case of ServerTrustPolicy now has equivalent types:
  • .performDefaultEvaluation is replaced by DefaultTrustEvaluator.
  • .performRevokedEvaluation is replaced by RevocationTrustEvaluator.
  • .pinCertificates is replaced by PinnedCertificatesTrustEvaluator.
  • .pinPublicKeys is replaced by PublicKeysTrustEvaluator.
  • .disableEvaluation is replaced by DisabledTrustEvaluator.
  • .customEvaluation is replaced by either using CompositeTrustEvaluator to combine existing ServerTrustEvaluating types or by creating a new type that conforms to ServerTrustEvaluating.
• DataResponse and DownloadResponse are now both doubly generic to both the response type as well as the error type. By default all Alamofire APIs return a AF prefixed response type, which defaults the Error type to AFError.
• Alamofire now returns AFError for all of its APIs, wrapping any underlying system or custom APIs in AFError instances.
• HTTPMethod is now a struct and not an enum and can be expanded to provide custom methods.
• HTTPHeaders and other types are now native Swift types rather than typealiases, so care must be taken when passing them to Obj-C bridged collections.
• AFError now has several new cases, so switching over it exhaustively will have to be updated.
• Notifications provided by Alamofire have had their keys renamed. You can now subscribe to:
  • Request.didResumeNotification and Request.didResumeTaskNotification to be notified when Requests and their URLSessionTasks have resume() called.
  • Request.didSuspendNotification and Request.didSuspendTaskNotification to be notified when Requests and their URLSessionTasks have suspend() called.
  • Request.didCancelNotification and Request.didCancelTaskNotification to be notified when Requests and their URLSessionTasks have cancel() called.
  • Request.didFinishNotification and Request.didCompleteTaskNotification to be notified when Requests have finish() called and when URLSessionTasks trigger the didComplete delegate method.
• MultipartFormData’s API has changed and the top level upload methods to create and upload MultipartFormData have been updated to match other request APIs, so it’s not longer necessary to deal with the Result of the multipart encoding.
• NetworkReachabilityManager has been refactored for greater reliability and simplicity. Instead of setting an update closure and then starting the listener, the closure is provided to the startListening method.
• Request and its various subclasses have been rewritten and the public API completely changed. Please see the documentation for an exhaustive list of the current functionality.
• Timeline and Alamofire’s previous URLSessionTaskMetrics handling have been replaced with native support for URLSessionTaskMetrics, which nows provides all timing information for Alamofire’s requests.
• cURL representations of Requests have been removed from the debugDescription, which is now useful for debug output, to a cURLDescription method which provides completion handler based access to the cURL command.
• DefaultDataResponse and DefaultDownloadResponse have been removed. All response methods now return the normal DataResponse or DownloadResponse types.
• Requirements for the DataResponseSerializerProtocol and DownloadResponseSerializer protocol have been changed from a property, serializeResponse, to a function, serializeResponse. This function can return a serialized value or throw an error, no longer requiring a Result return value. The new ResponseSerializer protocol combines the two previous protocols to simplify implementation.
• RequestAdapter has been updated to have an asynchronous requirement, allowing for access to async resources during request adaptation.

New Features

• Alamofire now vends its extensions of Swift and Foundation types through an af namespace.
• Serializers updated with more configuration options, including allowed empty response methods and codes, as well as the DataPreprocessor protocol, to prepare the received Data for serialization.
• RetryPolicy: A RequestRetrier to retry requests which failed due to system errors, such as network connectivity. Configurable with custom debounce settings and defaults to an extensive set of errors to make your requests more reliable.
• CachedResponseHandler: New protocol that provides control over whether a response is cached or not. The ResponseCacher type is provided as an easy to use implementation of the protocol.
• RedirectHandler: New protocol that provides control over a request’s redirect behavior. The Redirector type is provided as an easy to use implementation of the protocol.
• ParameterEncoder: New protocol that provides support for encoding Encodable values into URLRequests. JSONParameterEncoder and URLEncodedFormParameterEncoder are included with Alamofire.
• URLEncodedFormEncoder: An Encoder that produced URLEncodedForm strings.