Add map(to:) Operator (#126)

Author: danhalliday

CombineExt.xcodeproj/project.pbxproj

@@ -24,6 +24,8 @@
 /* Begin PBXBuildFile section */
 		1970A8AA25246FBD00799AB6 /* FilterMany.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1970A8A925246FBD00799AB6 /* FilterMany.swift */; };
 		1970A8B42524730500799AB6 /* FilterManyTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1970A8B32524730400799AB6 /* FilterManyTests.swift */; };
+		3793CBD428286BB20060441B /* MapTo.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3793CBD328286BB20060441B /* MapTo.swift */; };
+		3793CBD728286C090060441B /* MapToTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3793CBD528286BE90060441B /* MapToTests.swift */; };
 		712E36C82711B79000A2AAFE /* RetryWhen.swift in Sources */ = {isa = PBXBuildFile; fileRef = 712E36C72711B79000A2AAFE /* RetryWhen.swift */; };
 		7182326F26DAAF230026BAD3 /* RetryWhenTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 7182326E26DAAF230026BAD3 /* RetryWhenTests.swift */; };
 		BF330EF624F1FFFE001281FC /* CombineSchedulers in Frameworks */ = {isa = PBXBuildFile; productRef = BF330EF524F1FFFE001281FC /* CombineSchedulers */; };
@@ -110,6 +112,8 @@
 /* Begin PBXFileReference section */
 		1970A8A925246FBD00799AB6 /* FilterMany.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FilterMany.swift; sourceTree = "<group>"; };
 		1970A8B32524730400799AB6 /* FilterManyTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FilterManyTests.swift; sourceTree = "<group>"; };
+		3793CBD328286BB20060441B /* MapTo.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MapTo.swift; sourceTree = "<group>"; };
+		3793CBD528286BE90060441B /* MapToTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MapToTests.swift; sourceTree = "<group>"; };
 		712E36C72711B79000A2AAFE /* RetryWhen.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = RetryWhen.swift; sourceTree = "<group>"; };
 		7182326E26DAAF230026BAD3 /* RetryWhenTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RetryWhenTests.swift; sourceTree = "<group>"; };
 		BF330EF824F20032001281FC /* Timer.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Timer.swift; sourceTree = "<group>"; };
@@ -251,6 +255,7 @@
 				OBJ_23 /* FlatMapLatest.swift */,
 				OBJ_24 /* MapMany.swift */,
 				D836234724EA9446002353AC /* MergeMany.swift */,
+				3793CBD328286BB20060441B /* MapTo.swift */,
 				OBJ_25 /* Materialize.swift */,
 				C387777B24E6BBE900FAD2D8 /* Nwise.swift */,
 				OBJ_26 /* Partition.swift */,
@@ -300,6 +305,7 @@
 				OBJ_47 /* DematerializeTests.swift */,
 				OBJ_48 /* FlatMapLatestTests.swift */,
 				OBJ_49 /* MapManyTests.swift */,
+				3793CBD528286BE90060441B /* MapToTests.swift */,
 				1970A8B32524730400799AB6 /* FilterManyTests.swift */,
 				OBJ_50 /* MaterializeTests.swift */,
 				D836234924EA9888002353AC /* MergeManyTests.swift */,
@@ -573,6 +579,7 @@
 				OBJ_135 /* PrefixDurationTests.swift in Sources */,
 				OBJ_136 /* RemoveAllDuplicatesTests.swift in Sources */,
 				OBJ_137 /* ReplaySubjectTests.swift in Sources */,
+				3793CBD728286C090060441B /* MapToTests.swift in Sources */,
 				OBJ_138 /* SetOutputTypeTests.swift in Sources */,
 				OBJ_139 /* ShareReplayTests.swift in Sources */,
 				BFADDC8B25BCE91E00465E9B /* FlatMapBatchesTests.swift in Sources */,
@@ -590,6 +597,7 @@
 				OBJ_79 /* DemandBuffer.swift in Sources */,
 				OBJ_80 /* Sink.swift in Sources */,
 				OBJ_81 /* Optional.swift in Sources */,
+				3793CBD428286BB20060441B /* MapTo.swift in Sources */,
 				C387777C24E6BBE900FAD2D8 /* Nwise.swift in Sources */,
 				OBJ_82 /* Event.swift in Sources */,
 				OBJ_83 /* ObjectOwnership.swift in Sources */,

Sources/Operators/MapTo.swift

@@ -0,0 +1,22 @@
+//
+//  MapTo.swift
+//  CombineExt
+//
+//  Created by Dan Halliday on 08/05/2022.
+//  Copyright © 2022 Combine Community. All rights reserved.
+//
+
+#if canImport(Combine)
+import Combine
+
+@available(OSX 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
+public extension Publisher {
+    /// Replace each upstream value with a constant.
+    ///
+    /// - Parameter value: The constant with which to replace each upstream value.
+    /// - Returns: A new publisher wrapping the upstream, but with output type `Result`.
+    func map<Result>(to value: Result) -> Publishers.Map<Self, Result> {
+        map { _ in value }
+    }
+}
+#endif

Tests/MapToTests.swift

@@ -0,0 +1,32 @@
+//
+//  MapToTests.swift
+//  CombineExt
+//
+//  Created by Dan Halliday on 08/05/2022.
+//  Copyright © 2022 Combine Community. All rights reserved.
+//
+
+import Foundation
+
+#if !os(watchOS)
+import XCTest
+import Combine
+import CombineExt
+
+@available(OSX 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
+final class MapToTests: XCTestCase {
+    private var subscription: AnyCancellable!
+
+    func testMapToConstantValue() {
+        let subject = PassthroughSubject<Int, Never>()
+        var result: Int? = nil
+
+        subscription = subject
+            .map(to: 2)
+            .sink(receiveValue: { result = $0 })
+
+        subject.send(1)
+        XCTAssertEqual(result, 2)
+    }
+}
+#endif