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Added CurrentValuePublisher.flatMapLatest(_:) 
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Lines changed: 180 additions & 131 deletions

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‎Sources/CombineExtensions/CurrentValuePublisher/CurrentValuePublisher+FlatMapLatest.swift‎

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import Combine
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extension CurrentValuePublisher {
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/// Produces a new `CurrentValuePublisher` by transforming the current value and all subsequent
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/// values into new `CurrentValuePublisher` instances, and republishing the values emitted
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/// by the most recently transformed inner publisher.
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///
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/// Use this operator to dynamically switch between publishers based on the current value
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/// while maintaining a `CurrentValuePublisher` interface.
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///
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/// - Parameter transform: A closure that transforms a value to a new `CurrentValuePublisher`.
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/// - Returns: A `CurrentValuePublisher` that emits the values from the most recently
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/// transformed inner publisher.
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///
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/// - SeeAlso: `Publisher.flatMapLatest(_:)`
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public func flatMapLatest<T>(
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_ transform: @escaping (Output) -> CurrentValuePublisher<T, Failure>
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) -> CurrentValuePublisher<T, Failure> {
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let currentInnerPublisher = transform(value)
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switch (self.storage, currentInnerPublisher.storage) {
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case (.constant, .constant):
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// If the outer and inner publishers are both constant, we need to pass on this
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// characteristic to the outside by using the appropriate initializer.
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return CurrentValuePublisher<T, Failure>(value: currentInnerPublisher.value)
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default:
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let initial = currentInnerPublisher.value
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let upstream = Publishers.Merge(
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// The publisher of a single publisher of remaining values produced by the current
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// inner publisher (excluding its current value).
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Just(currentInnerPublisher.dropFirst().eraseToAnyPublisher())
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.setFailureType(to: Failure.self),
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// The publisher of subsequent inner publishers.
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self.dropFirst()
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.map(transform)
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.map { $0.eraseToAnyPublisher() }
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).switchToLatest()
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return CurrentValuePublisher<T, Failure>(
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initial: initial,
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upstream: upstream
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)
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}
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}
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}

‎Tests/CombineExtensionsTests/CurrentValuePublisher/CurrentValuePublisherTests.swift‎

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@@ -476,137 +476,137 @@ class CurrentValuePublisherTests: XCTestCase {
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XCTAssertEqual(values, ["1", "2"])
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}
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// // ============================================================================ //
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// // MARK: - FlatMap Operator
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// // ============================================================================ //
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//
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// func testFlatMap_constant_constant() {
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// var cancellables = Set<AnyCancellable>()
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// var values = [String]()
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//
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// CurrentValuePublisher(value: 1)
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// .flatMapLatest { CurrentValuePublisher(value: "\($0)") }
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// .sink { values.append($0) }
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// .store(in: &cancellables)
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//
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// XCTAssertEqual(values, ["1"])
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// }
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//
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// func testFlatMap_constant_subject() {
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// let subject = CurrentValueSubject<Int, Never>(1)
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// let publisher = subject.toCurrentValuePublisher()
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//
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// var cancellables = Set<AnyCancellable>()
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// var values = [String]()
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//
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// CurrentValuePublisher(value: ())
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// .flatMapLatest { _ in publisher.map { "\($0)" } }
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// .sink { values.append($0) }
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// .store(in: &cancellables)
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//
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// XCTAssertEqual(values, ["1"])
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//
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// subject.value = 2
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// XCTAssertEqual(values, ["1", "2"])
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// }
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//
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// func testFlatMap_subject_constants() {
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// let subject = CurrentValueSubject<Int, Never>(1)
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// let publisher = subject.toCurrentValuePublisher()
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//
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// var cancellables = Set<AnyCancellable>()
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// var values = [String]()
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//
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// publisher
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// .flatMapLatest { CurrentValuePublisher(value: "\($0)") }
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// .sink { values.append($0) }
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// .store(in: &cancellables)
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//
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// XCTAssertEqual(values, ["1"])
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//
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// subject.value = 2
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// XCTAssertEqual(values, ["1", "2"])
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//
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// subject.value = 2
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// XCTAssertEqual(values, ["1", "2", "2"])
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// }
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//
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// func testFlatMap_subject_subjects() {
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// let innerSubject1 = CurrentValueSubject<Int, Never>(10)
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// let innerPublisher1 = innerSubject1.toCurrentValuePublisher()
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//
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// let innerSubject2 = CurrentValueSubject<Int, Never>(20)
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// let innerPublisher2 = innerSubject2.toCurrentValuePublisher()
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//
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// let outerSubject = CurrentValueSubject<CurrentValuePublisher<Int, Never>, Never>(innerPublisher1)
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// let outerPublisher = outerSubject.toCurrentValuePublisher()
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//
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// var cancellables = Set<AnyCancellable>()
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// var values = [String]()
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//
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// outerPublisher
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// .flatMapLatest { innerPublisher in
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// innerPublisher.map { "\($0)" }
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// }
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// .sink { values.append($0) }
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// .store(in: &cancellables)
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//
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// XCTAssertEqual(values, ["10"])
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//
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// innerSubject1.value = 11
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// XCTAssertEqual(values, ["10", "11"])
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//
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// outerSubject.value = innerPublisher2
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// innerSubject2.value = 21
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// innerSubject2.value = 22
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// XCTAssertEqual(values, ["10", "11", "20", "21", "22"])
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//
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// innerSubject1.value = 12
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// outerSubject.value = innerPublisher1
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// innerSubject1.value = 13
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// XCTAssertEqual(values, ["10", "11", "20", "21", "22", "12", "13"])
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// }
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//
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// func testFlatMap_subject_subjectsAndConstants() {
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// let innerSubject1 = CurrentValueSubject<Int, Never>(10)
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// let innerPublisher1 = innerSubject1.toCurrentValuePublisher()
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//
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// let innerPublisher2 = CurrentValuePublisher<Int, Never>(value: 20)
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// let innerPublisher3 = CurrentValuePublisher<Int, Never>(value: 30)
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//
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// let outerSubject = CurrentValueSubject<CurrentValuePublisher<Int, Never>, Never>(innerPublisher1)
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// let outerPublisher = outerSubject.toCurrentValuePublisher()
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//
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// var cancellables = Set<AnyCancellable>()
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// var values = [String]()
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//
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// outerPublisher
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// .flatMapLatest { innerPublisher in
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// innerPublisher.map { "\($0)" }
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// }
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// .sink { values.append($0) }
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// .store(in: &cancellables)
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//
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// XCTAssertEqual(values, ["10"])
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//
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// innerSubject1.value = 11
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// XCTAssertEqual(values, ["10", "11"])
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//
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// outerSubject.value = innerPublisher2
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// XCTAssertEqual(values, ["10", "11", "20"])
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//
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// innerSubject1.value = 12
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// outerSubject.value = innerPublisher1
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// XCTAssertEqual(values, ["10", "11", "20", "12"])
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//
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// outerSubject.value = innerPublisher3
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// outerSubject.value = innerPublisher3
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// XCTAssertEqual(values, ["10", "11", "20", "12", "30", "30"])
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//
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// outerSubject.value = innerPublisher1
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// XCTAssertEqual(values, ["10", "11", "20", "12", "30", "30", "12"])
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// }
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//
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// ============================================================================ //
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// MARK: - FlatMapLatest Operator
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// ============================================================================ //
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func testFlatMapLatest_constant_constant() {
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var cancellables = Set<AnyCancellable>()
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var values = [String]()
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CurrentValuePublisher(value: 1)
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.flatMapLatest { CurrentValuePublisher(value: "\($0)") }
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.sink { values.append($0) }
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.store(in: &cancellables)
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XCTAssertEqual(values, ["1"])
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}
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func testFlatMapLatest_constant_subject() {
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let subject = CurrentValueSubject<Int, Never>(1)
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let publisher = CurrentValuePublisher(subject)
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var cancellables = Set<AnyCancellable>()
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var values = [String]()
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CurrentValuePublisher(value: ())
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.flatMapLatest { _ in publisher.map { "\($0)" } }
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.sink { values.append($0) }
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.store(in: &cancellables)
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XCTAssertEqual(values, ["1"])
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subject.value = 2
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XCTAssertEqual(values, ["1", "2"])
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}
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func testFlatMapLatest_subject_constants() {
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let subject = CurrentValueSubject<Int, Never>(1)
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let publisher = CurrentValuePublisher(subject)
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var cancellables = Set<AnyCancellable>()
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var values = [String]()
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publisher
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.flatMapLatest { CurrentValuePublisher(value: "\($0)") }
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.sink { values.append($0) }
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.store(in: &cancellables)
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XCTAssertEqual(values, ["1"])
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subject.value = 2
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XCTAssertEqual(values, ["1", "2"])
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subject.value = 2
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XCTAssertEqual(values, ["1", "2", "2"])
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}
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func testFlatMapLatest_subject_subjects() {
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let innerSubject1 = CurrentValueSubject<Int, Never>(10)
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let innerPublisher1 = CurrentValuePublisher(innerSubject1)
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let innerSubject2 = CurrentValueSubject<Int, Never>(20)
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let innerPublisher2 = CurrentValuePublisher(innerSubject2)
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let outerSubject = CurrentValueSubject<CurrentValuePublisher<Int, Never>, Never>(innerPublisher1)
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let outerPublisher = CurrentValuePublisher(outerSubject)
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var cancellables = Set<AnyCancellable>()
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var values = [String]()
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outerPublisher
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.flatMapLatest { innerPublisher in
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innerPublisher.map { "\($0)" }
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}
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.sink { values.append($0) }
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.store(in: &cancellables)
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XCTAssertEqual(values, ["10"])
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innerSubject1.value = 11
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XCTAssertEqual(values, ["10", "11"])
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outerSubject.value = innerPublisher2
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innerSubject2.value = 21
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innerSubject2.value = 22
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XCTAssertEqual(values, ["10", "11", "20", "21", "22"])
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innerSubject1.value = 12
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outerSubject.value = innerPublisher1
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innerSubject1.value = 13
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XCTAssertEqual(values, ["10", "11", "20", "21", "22", "12", "13"])
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}
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func testFlatMapLatest_subject_subjectsAndConstants() {
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let innerSubject1 = CurrentValueSubject<Int, Never>(10)
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let innerPublisher1 = CurrentValuePublisher(innerSubject1)
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let innerPublisher2 = CurrentValuePublisher<Int, Never>(value: 20)
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let innerPublisher3 = CurrentValuePublisher<Int, Never>(value: 30)
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let outerSubject = CurrentValueSubject<CurrentValuePublisher<Int, Never>, Never>(innerPublisher1)
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let outerPublisher = CurrentValuePublisher(outerSubject)
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var cancellables = Set<AnyCancellable>()
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var values = [String]()
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outerPublisher
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.flatMapLatest { innerPublisher in
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innerPublisher.map { "\($0)" }
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}
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.sink { values.append($0) }
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.store(in: &cancellables)
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XCTAssertEqual(values, ["10"])
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innerSubject1.value = 11
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XCTAssertEqual(values, ["10", "11"])
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outerSubject.value = innerPublisher2
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XCTAssertEqual(values, ["10", "11", "20"])
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innerSubject1.value = 12
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outerSubject.value = innerPublisher1
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XCTAssertEqual(values, ["10", "11", "20", "12"])
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outerSubject.value = innerPublisher3
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outerSubject.value = innerPublisher3
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XCTAssertEqual(values, ["10", "11", "20", "12", "30", "30"])
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outerSubject.value = innerPublisher1
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XCTAssertEqual(values, ["10", "11", "20", "12", "30", "30", "12"])
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}
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// // ============================================================================ //
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// // MARK: - Remove Duplicates Operator
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// // ============================================================================ //

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