Merge pull request #635 from Marcocanc/feature/observable-bindingtarget

Add binding operator to Signal.Observer

Author: mdiep

CHANGELOG.md

@@ -1,7 +1,7 @@
 # master
 *Please add new entries at the top.*
 1. Fixed Result extensions ambiguity (#733, kudos to @nekrich)
-
+1. Add `<~` binding operator to `Signal.Observer` (#635, kudos to @Marcocanc)
 
 # 6.0.0
 1. Dropped support for Swift 4.2 (Xcode 9)

Sources/UnidirectionalBinding.swift

@@ -102,6 +102,33 @@ extension BindingTargetProvider {
 	}
 }
 
+extension Signal.Observer {
+	/// Binds a source to a target, updating the target's value to the latest
+	/// value sent by the source.
+	///
+	/// - note: Only `value` events will be forwarded to the Observer.
+	///         The binding will automatically terminate when the target is
+	///         deinitialized, or when the source sends a `completed` event.
+	///
+	/// - parameters:
+	///   - target: A target to be bond to.
+	///   - source: A source to bind.
+	///
+	/// - returns: A disposable that can be used to terminate binding before the
+	///            deinitialization of the target or the source's `completed`
+	///            event.
+	@discardableResult
+	public static func <~
+		<Source: BindingSource>
+		(observer: Signal<Value, Error>.Observer, source: Source) -> Disposable?
+		where Source.Value == Value
+	{
+		return source.producer.startWithValues { [weak observer] in
+			observer?.send(value: $0)
+		}
+	}
+}
+
 /// A binding target that can be used with the `<~` operator.
 public struct BindingTarget<Value>: BindingTargetProvider {
 	public let lifetime: Lifetime

Tests/ReactiveSwiftTests/UnidirectionalBindingSpec.swift

@@ -201,6 +201,18 @@ class UnidirectionalBindingSpec: QuickSpec {
 				expect(value).toEventually(equal(2))
 				expect(mainQueueCounter.value).toEventually(equal(2))
 			}
+
+			describe("observer binding operator") {
+				it("should forward values to observer") {
+					let targetPipe = Signal<Int?, Never>.pipe()
+					let sourcePipe = Signal<Int?, Never>.pipe()
+					let targetProperty = Property<Int?>(initial: nil, then: targetPipe.output)
+					targetPipe.input <~ sourcePipe.output
+					expect(targetProperty.value).to(beNil())
+					sourcePipe.input.send(value: 1)
+					expect(targetProperty.value).to(equal(1))
+				}
+			}
 		}
 	}
 }