Pick Transition (#27)

Author: davdroman

Sources/AtomicTransition/Asymmetric.swift renamed to Sources/AtomicTransition/On.swift

@@ -1,41 +1,5 @@
 import class UIKit.UIView
 
-/// A composite transition that uses a different transition for push versus pop.
-public struct Asymmetric<InsertionTransition: AtomicTransition, RemovalTransition: AtomicTransition>: AtomicTransition {
-    private let insertion: InsertionTransition
-    private let removal: RemovalTransition
-
-    private init(insertion: InsertionTransition, removal: RemovalTransition) {
-        self.insertion = insertion
-        self.removal = removal
-    }
-
-    public init(
-        @AtomicTransitionBuilder insertion: () -> InsertionTransition,
-        @AtomicTransitionBuilder removal: () -> RemovalTransition
-    ) {
-        self.init(insertion: insertion(), removal: removal())
-    }
-
-    public func transition(_ view: TransientView, for operation: TransitionOperation, in container: Container) {
-        switch operation {
-        case .insertion:
-            insertion.transition(view, for: operation, in: container)
-        case .removal:
-            removal.transition(view, for: operation, in: container)
-        }
-    }
-}
-
-extension Asymmetric: MirrorableAtomicTransition where InsertionTransition: MirrorableAtomicTransition, RemovalTransition: MirrorableAtomicTransition {
-    public func mirrored() -> Asymmetric<InsertionTransition.Mirrored, RemovalTransition.Mirrored> {
-        return .init(insertion: insertion.mirrored(), removal: removal.mirrored())
-    }
-}
-
-extension Asymmetric: Equatable where InsertionTransition: Equatable, RemovalTransition: Equatable {}
-extension Asymmetric: Hashable where InsertionTransition: Hashable, RemovalTransition: Hashable {}
-
 /// A transition that executes only on insertion.
 public struct OnInsertion<Transition: AtomicTransition>: AtomicTransition {
     private let transition: Transition

Sources/NavigationTransition/Combined.swift

@@ -4,6 +4,14 @@ extension AnyNavigationTransition {
     public func combined(with other: Self) -> Self {
         switch (self.handler, other.handler) {
         case (.transient(let lhsHandler), .transient(let rhsHandler)):
+            struct Erased: NavigationTransition {
+                let handler: AnyNavigationTransition.TransientHandler
+
+                @inlinable
+                func transition(from fromView: TransientView, to toView: TransientView, for operation: TransitionOperation, in container: Container) {
+                    handler(fromView, toView, operation, container)
+                }
+            }
             return AnyNavigationTransition(
                 Combined(Erased(handler: lhsHandler), Erased(handler: rhsHandler))
             )

Sources/NavigationTransition/Erased.swift

@@ -18,6 +18,9 @@ public struct MirrorPush<Transition: MirrorableAtomicTransition>: NavigationTran
     }
 }
 
+extension MirrorPush: Equatable where Transition: Equatable {}
+extension MirrorPush: Hashable where Transition: Hashable {}
+
 /// Used to define a transition that executes on pop, and executes the mirrored version of said transition on push.
 public struct MirrorPop<Transition: MirrorableAtomicTransition>: NavigationTransition {
     private let transition: Transition
@@ -35,3 +38,6 @@ public struct MirrorPop<Transition: MirrorableAtomicTransition>: NavigationTrans
         }
     }
 }
+
+extension MirrorPop: Equatable where Transition: Equatable {}
+extension MirrorPop: Hashable where Transition: Hashable {}

Sources/NavigationTransition/Mirror.swift

@@ -1,36 +1,5 @@
 import AtomicTransition
 
-/// A composite transition that uses a different transition for push versus pop.
-public struct Asymmetric<PushTransition: NavigationTransition, PopTransition: NavigationTransition>: NavigationTransition {
-    private let push: PushTransition
-    private let pop: PopTransition
-
-    public init(
-        @AtomicTransitionBuilder push: () -> PushTransition,
-        @AtomicTransitionBuilder pop: () -> PopTransition
-    ) {
-        self.push = push()
-        self.pop = pop()
-    }
-
-    public func transition(
-        from fromView: TransientView,
-        to toView: TransientView,
-        for operation: TransitionOperation,
-        in container: Container
-    ) {
-        switch operation {
-        case .push:
-            push.transition(from: fromView, to: toView, for: operation, in: container)
-        case .pop:
-            pop.transition(from: fromView, to: toView, for: operation, in: container)
-        }
-    }
-}
-
-extension Asymmetric: Equatable where PushTransition: Equatable, PopTransition: Equatable {}
-extension Asymmetric: Hashable where PushTransition: Hashable, PopTransition: Hashable {}
-
 /// Used to define a transition that executes only on push.
 public struct OnPush<Transition: AtomicTransition>: NavigationTransition {
     private let transition: Transition

Sources/NavigationTransition/Asymmetric.swift renamed to Sources/NavigationTransition/On.swift

@@ -0,0 +1,51 @@
+/// Used to isolate the push portion of a full `NavigationTransition` and execute it on push, ignoring the pop portion.
+public struct PickPush<Transition: NavigationTransition>: NavigationTransition {
+    private let transition: Transition
+
+    public init(@NavigationTransitionBuilder transition: () -> Transition) {
+        self.transition = transition()
+    }
+
+    public func transition(
+        from fromView: TransientView,
+        to toView: TransientView,
+        for operation: TransitionOperation,
+        in container: Container
+    ) {
+        switch operation {
+        case .push:
+            transition.transition(from: fromView, to: toView, for: operation, in: container)
+        case .pop:
+            return
+        }
+    }
+}
+
+extension PickPush: Equatable where Transition: Equatable {}
+extension PickPush: Hashable where Transition: Hashable {}
+
+/// Used to isolate the pop portion of a full `NavigationTransition` and execute it on pop, ignoring the push portion.
+public struct PickPop<Transition: NavigationTransition>: NavigationTransition {
+    private let transition: Transition
+
+    public init(@NavigationTransitionBuilder transition: () -> Transition) {
+        self.transition = transition()
+    }
+
+    public func transition(
+        from fromView: TransientView,
+        to toView: TransientView,
+        for operation: TransitionOperation,
+        in container: Container
+    ) {
+        switch operation {
+        case .push:
+            return
+        case .pop:
+            transition.transition(from: fromView, to: toView, for: operation, in: container)
+        }
+    }
+}
+
+extension PickPop: Equatable where Transition: Equatable {}
+extension PickPop: Hashable where Transition: Hashable {}

Sources/NavigationTransition/Pick.swift

@@ -1,28 +1,6 @@
 @_spi(package) import AtomicTransition
 import TestUtils
 
-final class AsymmetricTests: XCTestCase {
-    func testInsertion() {
-        let expectation = expectation(description: "Handler called")
-        let sut = Asymmetric(
-            insertion: { Spy { expectation.fulfill() } },
-            removal: { Spy { XCTFail() } }
-        )
-        sut.transition(.unimplemented, for: .insertion, in: .unimplemented)
-        wait(for: [expectation], timeout: 0)
-    }
-
-    func testRemoval() {
-        let expectation = expectation(description: "Handler called")
-        let sut = Asymmetric(
-            insertion: { Spy { XCTFail() } },
-            removal: { Spy { expectation.fulfill() } }
-        )
-        sut.transition(.unimplemented, for: .removal, in: .unimplemented)
-        wait(for: [expectation], timeout: 0)
-    }
-}
-
 final class OnInsertionTests: XCTestCase {
     func testInsertion() {
         let expectation = expectation(description: "Handler called")