Added mapTo for Single and Maybe (#221)

Author: M0rtyMerr

CHANGELOG.md

@@ -7,6 +7,7 @@ Changelog
 - `once` now uses a `NSRecursiveLock` instead of the deprecated `OSAtomicOr32OrigBarrier`
 - added `merge(with:)` for `Observable`
 - removed `flatMapSync` operator
+- added `mapTo` for `Single` and `Maybe`
 - added SPM support
 
 5.0.0

Source/RxSwift/mapTo.swift

@@ -17,7 +17,31 @@ extension ObservableType {
 	- parameter value: A constant that each element of the input sequence is being replaced with
 	- returns: An observable sequence containing the values `value` provided as a parameter
 	*/
-	public func mapTo<R>(_ value: R) -> Observable<R> {
+	public func mapTo<Result>(_ value: Result) -> Observable<Result> {
 		return map { _ in value }
 	}
 }
+
+extension PrimitiveSequence where Trait == SingleTrait {
+    /**
+     Returns a Single which success event is mapped to constant provided as a parameter
+
+     - parameter value: A constant that element of the input sequence is being replaced with
+     - returns: A Single containing the value `value` provided as a parameter in case of success
+     */
+    public func mapTo<Result>(_ value: Result) -> Single<Result> {
+        return map { _ in value }
+    }
+}
+
+extension PrimitiveSequence where Trait == MaybeTrait {
+    /**
+     Returns a Maybe which success event is mapped to constant provided as a parameter
+
+     - parameter value: A constant that element of the input sequence is being replaced with
+     - returns: A Maybe containing the value `value` provided as a parameter in case of success
+     */
+    public func mapTo<Result>(_ value: Result) -> Maybe<Result> {
+        return map { _ in value }
+    }
+}

Tests/RxSwift/mapToTests.swift

@@ -14,7 +14,7 @@ import RxTest
 
 class MapToTests: XCTestCase {
 
-    let numbers: [Int?] = [1, nil, Int?(3)]
+    private let numbers: [Int?] = [1, nil, Int?(3)]
     private var observer: TestableObserver<String>!
 
     override func setUp() {
@@ -48,3 +48,72 @@ class MapToTests: XCTestCase {
         XCTAssertEqual(observer.events, correctValues)
     }
 }
+
+// MARK: - Single
+extension MapToTests {
+    func testSingleReplaceSuccess() {
+        // Given
+        let expectedValue = "candy"
+        let scheduler = TestScheduler(initialClock: 0)
+        // When
+        let result = scheduler.start {
+            Single.just(1).mapTo(expectedValue).asObservable()
+        }
+        // Then
+        XCTAssertEqual(result.events, [
+            .next(TestScheduler.Defaults.subscribed, expectedValue),
+            .completed(TestScheduler.Defaults.subscribed)
+        ])
+    }
+
+    func testSingleNoReplaceFailure() {
+        // Given
+        let scheduler = TestScheduler(initialClock: 0)
+        // When
+        let result = scheduler.start {
+            Single<Int>.error(testError).mapTo("candy").asObservable()
+        }
+        // Then
+        XCTAssertEqual(result.events, [.error(TestScheduler.Defaults.subscribed, testError)])
+    }
+}
+
+// MARK: - Maybe
+extension MapToTests {
+    func testMaybeReplaceSuccess() {
+        // Given
+        let expectedValue = "candy"
+        let scheduler = TestScheduler(initialClock: 0)
+        // When
+        let result = scheduler.start {
+            Maybe.just(1).mapTo(expectedValue).asObservable()
+        }
+        // Then
+        XCTAssertEqual(result.events, [
+            .next(TestScheduler.Defaults.subscribed, expectedValue),
+            .completed(TestScheduler.Defaults.subscribed)
+        ])
+    }
+
+    func testMaybeNoReplaceFailure() {
+        // Given
+        let scheduler = TestScheduler(initialClock: 0)
+        // When
+        let result = scheduler.start {
+            Maybe<Int>.error(testError).mapTo("candy").asObservable()
+        }
+        // Then
+        XCTAssertEqual(result.events, [.error(TestScheduler.Defaults.subscribed, testError)])
+    }
+
+    func testMaybeNoReplaceEmpty() {
+        // Given
+        let scheduler = TestScheduler(initialClock: 0)
+        // When
+        let result = scheduler.start {
+            Maybe<Int>.empty().mapTo("candy").asObservable()
+        }
+        // Then
+        XCTAssertEqual(result.events, [.completed(TestScheduler.Defaults.subscribed)])
+    }
+}