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Add CompositeEventSourceBuilder #28
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jeppes
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spotify:master
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JensAyton:composite-event-source-builder
May 27, 2019
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61 changes: 61 additions & 0 deletions
61
MobiusCore/Source/EventSources/CompositeEventSourceBuilder.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,61 @@ | ||
| // Copyright (c) 2019 Spotify AB. | ||
| // | ||
| // Licensed to the Apache Software Foundation (ASF) under one | ||
| // or more contributor license agreements. See the NOTICE file | ||
| // distributed with this work for additional information | ||
| // regarding copyright ownership. The ASF licenses this file | ||
| // to you under the Apache License, Version 2.0 (the | ||
| // "License"); you may not use this file except in compliance | ||
| // with the License. You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
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| /// A `CompositeEventSourceBuilder` gathers the provided event sources together and builds a single event source that | ||
| /// subscribes to all of them when its `subscribe` method is called. | ||
| public struct CompositeEventSourceBuilder<Event> { | ||
| private let eventSources: [AnyEventSource<Event>] | ||
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| /// Initializes a `CompositeEventSourceBuilder`. | ||
| public init() { | ||
| self.init(eventSources: []) | ||
| } | ||
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| private init(eventSources: [AnyEventSource<Event>]) { | ||
| self.eventSources = eventSources | ||
| } | ||
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| /// Returns a new `CompositeEventSourceBuilder` with the specified event source added to it. | ||
| public func addEventSource<Source: EventSource>(_ source: Source) | ||
| -> CompositeEventSourceBuilder<Event> where Source.Event == Event { | ||
| let sources = eventSources + [AnyEventSource<Event>(source)] | ||
| return CompositeEventSourceBuilder(eventSources: sources) | ||
| } | ||
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| /// Builds an event source that composes all the event sources that have been added to the builder. | ||
| /// | ||
| /// - Returns: An event source which represents the composition of the builder’s input event sources. The type | ||
| /// of this source is an implementation detail; consumers should avoid spelling it out if possible. | ||
| public func build() -> AnyEventSource<Event> { | ||
| switch eventSources.count { | ||
| case 0: | ||
| return AnyEventSource<Event> { _ in AnonymousDisposable {} } | ||
| case 1: | ||
| return eventSources[0] | ||
| default: | ||
| let eventSources = self.eventSources | ||
| return AnyEventSource { consumer in | ||
| let disposables = eventSources.map { | ||
| $0.subscribe(consumer: consumer) | ||
| } | ||
| return CompositeDisposable(disposables: disposables) | ||
| } | ||
| } | ||
| } | ||
| } | ||
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139 changes: 139 additions & 0 deletions
139
MobiusCore/Test/EventSources/CompositeEventSourceBuilderTests.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| // Copyright (c) 2019 Spotify AB. | ||
| // | ||
| // Licensed to the Apache Software Foundation (ASF) under one | ||
| // or more contributor license agreements. See the NOTICE file | ||
| // distributed with this work for additional information | ||
| // regarding copyright ownership. The ASF licenses this file | ||
| // to you under the Apache License, Version 2.0 (the | ||
| // "License"); you may not use this file except in compliance | ||
| // with the License. You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
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| @testable import MobiusCore | ||
| import Nimble | ||
| import Quick | ||
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| class CompositeEventSourceBuilderTest: QuickSpec { | ||
| // swiftlint:disable function_body_length | ||
| override func spec() { | ||
| var eventsReceived: [Int]! | ||
| var compositeEventSource: AnyEventSource<Int>! | ||
| var disposable: Disposable! | ||
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| describe("CompositeEventSourceBuilder") { | ||
| context("when configuring the composite event source builder") { | ||
| context("with no event sources") { | ||
| beforeEach { | ||
| let sut = CompositeEventSourceBuilder<Int>() | ||
| compositeEventSource = sut.build() | ||
| eventsReceived = [] | ||
| } | ||
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| it("should produce an event source") { | ||
| // In particular, we want a do-nothing event source rather than an assertion or crash. | ||
| disposable = compositeEventSource.subscribe { | ||
| eventsReceived.append($0) | ||
| } | ||
| disposable.dispose() | ||
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| expect(eventsReceived).to(equal([])) | ||
| } | ||
| } | ||
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| context("with one event source") { | ||
| var eventSource: TestEventSource! | ||
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| beforeEach { | ||
| eventSource = TestEventSource() | ||
| let sut = CompositeEventSourceBuilder<Int>() | ||
| .addEventSource(eventSource) | ||
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| compositeEventSource = sut.build() | ||
| eventsReceived = [] | ||
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| disposable = compositeEventSource.subscribe { | ||
| eventsReceived.append($0) | ||
| } | ||
| } | ||
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| it("should provide an event source equivalent to the input event source") { | ||
| eventSource.dispatch(1) | ||
| eventSource.dispatch(2) | ||
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| let expectedEvents = [1, 2] | ||
| expect(eventsReceived).to(equal(expectedEvents)) | ||
| } | ||
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| it("should return a disposable that disposes the original event source") { | ||
| disposable?.dispose() | ||
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| expect(eventSource.isDisposed).to(beTrue()) | ||
| } | ||
| } | ||
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| context("with several event sources") { | ||
| var eventSources: [TestEventSource]! | ||
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| beforeEach { | ||
| eventSources = [TestEventSource(), TestEventSource(), TestEventSource()] | ||
| var sut = CompositeEventSourceBuilder<Int>() | ||
| eventSources.forEach { | ||
| sut = sut.addEventSource($0) | ||
| } | ||
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| compositeEventSource = sut.build() | ||
| eventsReceived = [] | ||
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| disposable = compositeEventSource.subscribe { | ||
| eventsReceived.append($0) | ||
| } | ||
| } | ||
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| it("should produce an event source that emits the events from all input sources") { | ||
| eventSources.enumerated().forEach { index, source in | ||
| source.dispatch(index) | ||
| } | ||
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| let expectedEvents = [0, 1, 2] | ||
| expect(eventsReceived).to(equal(expectedEvents)) | ||
| } | ||
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| it("should return a disposable that disposes of all the input event sources") { | ||
| disposable?.dispose() | ||
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| eventSources.forEach { | ||
| expect($0.isDisposed).to(beTrue()) | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| private class TestEventSource: EventSource, Disposable { | ||
| typealias Event = Int | ||
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| var consumer: Consumer<Int>? | ||
| func subscribe(consumer: @escaping Consumer<Int>) -> Disposable { | ||
| self.consumer = consumer | ||
| return self | ||
| } | ||
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| var isDisposed = false | ||
| func dispose() { | ||
| isDisposed = true | ||
| } | ||
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| func dispatch(_ event: Int) { | ||
| consumer?(event) | ||
| } | ||
| } |
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In particular, I’d like the return type to be
some EventSource<.Event == Event>, but Swift 5.1 will only have unconstrained opaque types.