Repeater timing (#9)

Author: quickthyme

Sources/QLoop/QLAnchor+ConvenienceInit.swift

@@ -12,22 +12,46 @@ public extension QLAnchor {
                   onError: QLAnchor.emptyErr)
     }
 
-    convenience init(repeaters: QLAnchor...) {
+    convenience init(earlyRepeaters: QLAnchor...) {
         self.init(echoFilter: QLAnchor.DefaultEchoFilter,
-                  repeaters: repeaters)
+                  earlyRepeaters: earlyRepeaters,
+                  lateRepeaters: [])
+    }
+
+    convenience init(lateRepeaters: QLAnchor...) {
+        self.init(echoFilter: QLAnchor.DefaultEchoFilter,
+                  earlyRepeaters: [],
+                  lateRepeaters: lateRepeaters)
+    }
+
+    convenience init(earlyRepeaters: [QLAnchor],
+                     lateRepeaters: [QLAnchor]) {
+        self.init(echoFilter: QLAnchor.DefaultEchoFilter,
+                  earlyRepeaters: earlyRepeaters,
+                  lateRepeaters: lateRepeaters)
+    }
+
+    convenience init(echoFilter: @escaping EchoFilter,
+                     earlyRepeaters: QLAnchor...) {
+        self.init(echoFilter: echoFilter,
+                  earlyRepeaters: earlyRepeaters,
+                  lateRepeaters: [])
     }
 
     convenience init(echoFilter: @escaping EchoFilter,
-                     repeaters: QLAnchor...) {
+                     lateRepeaters: QLAnchor...) {
         self.init(echoFilter: echoFilter,
-                  repeaters: repeaters)
+                  earlyRepeaters: [],
+                  lateRepeaters: lateRepeaters)
     }
 
     convenience init(echoFilter: @escaping EchoFilter,
-                     repeaters: [QLAnchor]) {
+                     earlyRepeaters: [QLAnchor],
+                     lateRepeaters: [QLAnchor]) {
         self.init(onChange: QLAnchor.emptyIn,
                   onError: QLAnchor.emptyErr)
-        self.repeaters = repeaters
+        self.addRepeaters(earlyRepeaters, timing: .early)
+        self.addRepeaters(lateRepeaters, timing: .late)
         self.echoFilter = echoFilter
     }
 }

Sources/QLoop/QLAnchor.swift

@@ -11,17 +11,28 @@ public final class QLAnchor<Input>: AnyAnchor {
     public typealias EchoFilter = (Input?, QLAnchor<Input>) -> (Bool)
     internal static var DefaultEchoFilter: EchoFilter { return { _, _ in return true } }
 
+    public enum Timing {
+        case early, late
+    }
+
     internal final class Repeater {
+
         weak var anchor: QLAnchor?
-        init(_ anchor: QLAnchor) {
+
+        let timing: Timing
+
+        init(_ anchor: QLAnchor, timing: Timing) {
+            self.timing = timing
             self.anchor = anchor
         }
-        func echo(value: Input?, filter: EchoFilter) {
+
+        func echo(value: Input?, filter: EchoFilter, timing: Timing) {
             if let repeater = self.anchor,
                 filter(value, repeater) {
                 repeater.value = value
             }
         }
+
         func echo(error: Error) {
             anchor?.error = error
         }
@@ -42,9 +53,13 @@ public final class QLAnchor<Input>: AnyAnchor {
 
     public var inputSegment: AnySegment?
 
-    public var repeaters: [QLAnchor] {
-        get { return _repeaters.compactMap { $0.anchor } }
-        set { self._repeaters = newValue.map { Repeater($0) } }
+    public func addRepeaters(_ repeaters: [QLAnchor], timing: Timing) {
+        let repeaters = repeaters.map { Repeater($0, timing: timing) }
+        self._repeaters.append(contentsOf: repeaters)
+    }
+
+    public func getRepeaters(timing: Timing) -> [QLAnchor] {
+        return _repeaters.compactMap { ($0.timing == timing) ? $0.anchor : nil }
     }
 
     internal var _repeaters: [Repeater] = []
@@ -64,8 +79,9 @@ public final class QLAnchor<Input>: AnyAnchor {
             if let err = getReroutableError(newValue) {
                 self.error = err
             } else {
+                echo(value: newValue, timing: .early)
                 dispatch(value: newValue)
-                echo(value: newValue)
+                echo(value: newValue, timing: .late)
             }
 
             if (QLCommon.Config.Anchor.releaseValues) {
@@ -113,9 +129,10 @@ public final class QLAnchor<Input>: AnyAnchor {
         }
     }
 
-    private func echo(value: Input?) {
+    private func echo(value: Input?, timing: Timing) {
         for repeater in _repeaters {
-            repeater.echo(value: value, filter: echoFilter)
+            guard repeater.timing == timing else { continue }
+            repeater.echo(value: value, filter: echoFilter, timing: timing)
         }
     }
 

Tests/QLoopTests/QLAnchorTests.swift

@@ -81,7 +81,7 @@ final class QLAnchorTests: XCTestCase {
         XCTAssert((receivedError as? QLCommon.Error) == QLCommon.Error.ThrownButNotSet)
     }
 
-    func test_given_it_has_repeaters_with_default_filter_when_input_set_then_it_echoes_to_them_as_well() {
+    func test_given_it_has_early_repeaters_with_default_filter_when_input_set_then_it_echoes_to_them_as_well() {
         var receivedVal0: Int = -1
         var receivedVal1: Int = -1
         var receivedVal2: Int = -1
@@ -90,7 +90,30 @@ final class QLAnchorTests: XCTestCase {
         let expectRepeater2 = expectation(description: "should echo value to repeater2")
         let repeater1 = QLAnchor<Int>(onChange: { receivedVal1 = $0!; expectRepeater1.fulfill() })
         let repeater2 = QLAnchor<Int>(onChange: { receivedVal2 = $0!; expectRepeater2.fulfill() })
-        let subject = QLAnchor<Int>(repeaters: repeater1, repeater2)
+        let subject = QLAnchor<Int>(earlyRepeaters: repeater1, repeater2)
+        XCTAssertEqual(subject.getRepeaters(timing: .early).count, 2)
+
+        subject.onChange = { receivedVal0 = $0!; expectOriginal0.fulfill() }
+
+        subject.value = 99
+
+        wait(for: [expectOriginal0, expectRepeater1, expectRepeater2], timeout: 8.0)
+        XCTAssertEqual(receivedVal0, 99)
+        XCTAssertEqual(receivedVal1, 99)
+        XCTAssertEqual(receivedVal2, 99)
+    }
+
+    func test_given_it_has_late_repeaters_with_default_filter_when_input_set_then_it_echoes_to_them_as_well() {
+        var receivedVal0: Int = -1
+        var receivedVal1: Int = -1
+        var receivedVal2: Int = -1
+        let expectOriginal0 = expectation(description: "should dispatch value")
+        let expectRepeater1 = expectation(description: "should echo value to repeater1")
+        let expectRepeater2 = expectation(description: "should echo value to repeater2")
+        let repeater1 = QLAnchor<Int>(onChange: { receivedVal1 = $0!; expectRepeater1.fulfill() })
+        let repeater2 = QLAnchor<Int>(onChange: { receivedVal2 = $0!; expectRepeater2.fulfill() })
+        let subject = QLAnchor<Int>(lateRepeaters: repeater1, repeater2)
+        XCTAssertEqual(subject.getRepeaters(timing: .late).count, 2)
 
         subject.onChange = { receivedVal0 = $0!; expectOriginal0.fulfill() }
 
@@ -113,7 +136,9 @@ final class QLAnchorTests: XCTestCase {
                                       onError: { receivedErr1 = $0; expectRepeater1.fulfill() })
         let repeater2 = QLAnchor<Int>(onChange: { _ in },
                                       onError: { receivedErr2 = $0; expectRepeater2.fulfill() })
-        let subject = QLAnchor<Int>(repeaters: repeater1, repeater2)
+        let subject = QLAnchor<Int>(earlyRepeaters: [repeater1], lateRepeaters: [repeater2])
+        XCTAssertEqual(subject.getRepeaters(timing: .early).count, 1)
+        XCTAssertEqual(subject.getRepeaters(timing: .late).count, 1)
 
         subject.onError = { receivedErr0 = $0; expectOriginal0.fulfill() }
 
@@ -125,7 +150,34 @@ final class QLAnchorTests: XCTestCase {
         XCTAssertNotNil(receivedErr2)
     }
 
-    func test_given_it_has_repeaters_with_custom_filter_when_input_set_then_it_dispatches_then_echoes_to_them_conditionally() {
+    func test_given_it_has_earlyRepeaters_with_custom_filter_when_input_set_then_it_dispatches_then_echoes_to_them_conditionally() {
+        var receivedVal0: Int = -1
+        var receivedVal1: Int = -1
+        var receivedVal2: Int = -1
+        let expectOriginal0 = expectation(description: "should dispatch value")
+        let expectRepeater2 = expectation(description: "should echo value to repeater2")
+        let repeater1 = QLAnchor<Int>(onChange: { receivedVal1 = $0! })
+        let repeater2 = QLAnchor<Int>(onChange: { receivedVal2 = $0!; expectRepeater2.fulfill() })
+
+        let subject = QLAnchor<Int>(
+            echoFilter: ({ val, repeater in
+                return (val == 11 && repeater === repeater1)
+                    || (val == 22 && repeater === repeater2)
+            }),
+            earlyRepeaters: repeater1, repeater2
+        )
+
+        subject.onChange = { receivedVal0 = $0!; expectOriginal0.fulfill() }
+
+        subject.value = 22
+
+        wait(for: [expectOriginal0, expectRepeater2], timeout: 8.0)
+        XCTAssertEqual(receivedVal0, 22)
+        XCTAssertEqual(receivedVal1, -1)
+        XCTAssertEqual(receivedVal2, 22)
+    }
+
+    func test_given_it_has_lateRepeaters_with_custom_filter_when_input_set_then_it_dispatches_then_echoes_to_them_conditionally() {
         var receivedVal0: Int = -1
         var receivedVal1: Int = -1
         var receivedVal2: Int = -1
@@ -139,7 +191,7 @@ final class QLAnchorTests: XCTestCase {
                 return (val == 11 && repeater === repeater1)
                     || (val == 22 && repeater === repeater2)
             }),
-            repeaters: repeater1, repeater2
+            lateRepeaters: repeater1, repeater2
         )
 
         subject.onChange = { receivedVal0 = $0!; expectOriginal0.fulfill() }

docs/changelog.md

@@ -5,6 +5,12 @@
 ## Change Log
 
 
+<br />
+
+### 0.1.7
+
+- `QLAnchor` repeater timing (early/late)
+
 <br />
 
 ### 0.1.6

docs/reference/QLAnchor.md

@@ -20,7 +20,9 @@
 
 - init(onChange: `(Input?)->()`, onError: `(Error)->()` )
 
-- init(repeaters: `QLAnchor.Repeater`, `...` )
+- init(earlyRepeaters: `QLAnchor.Repeater`, `...` )
+
+- init(lateRepeaters: `QLAnchor.Repeater`, `...` )
 
 
 <br />
@@ -75,9 +77,9 @@ Repeaters offer a way to fork multiple streams off of the main path.
 When an Anchor has repeaters applied, then it will `echo` any `value` and `error` changes
 to each of them.
 
-By default, it forwards all changes to all repeaters. In order to make it conditional, we can
-set an `EchoFilter`, which gets called prior to forwarding to each repeater. Return `false`
-from the EchoFilter to block that repeater from receiving the change.
+By default, it forwards all changes to all repeaters. In order to make it conditional,
+include an `EchoFilter`. Return `false` from the EchoFilter to block that repeater
+from receiving the change.
 
 
 ##### EchoFilter