Implement node ref updates in TestRenderer (#51)

This is a prerequisite for #49, the actual `UIKitRenderer` implementation will follow in a separate PR.

Sources/Tokamak/AnyNode.swift

@@ -15,7 +15,7 @@ public struct AnyNode: Equatable {
       lhs.props == rhs.props
   }
 
-  let ref: AnyObject?
+  public let ref: AnyObject?
   public let props: AnyEquatable
   public let children: AnyEquatable
   let type: ComponentType
@@ -115,7 +115,7 @@ extension CompositeComponent {
 
 extension RefComponent {
   public static func node(
-    ref: Ref<RefType>,
+    ref: Ref<RefTarget?>,
     _ props: Props,
     _ children: Children
   ) -> AnyNode {

Sources/Tokamak/Components.swift

@@ -13,8 +13,24 @@ public protocol AnyHostComponent {}
 
 public protocol HostComponent: AnyHostComponent, Component {}
 
-public protocol RefComponent: HostComponent {
-  associatedtype RefType
+public protocol AnyRefComponent {
+  static func update(ref: AnyObject, with value: Any)
+}
+
+public protocol RefComponent: AnyRefComponent, HostComponent {
+  associatedtype RefTarget
+}
+
+extension AnyRefComponent where Self: RefComponent {
+  public static func update(ref: AnyObject, with value: Any) {
+    guard let ref = ref as? Ref<RefTarget?>,
+      let value = value as? RefTarget else {
+      assertionFailure("failed to cast objects passed to \(#function)")
+      return
+    }
+
+    ref.value = value
+  }
 }
 
 /// Type-erased version of `CompositeComponent` to work around

Sources/TokamakTestRenderer/TestRenderer.swift

@@ -28,13 +28,21 @@ public final class TestRenderer: Renderer {
     let result = TestView(component.node)
     parent.add(subview: result)
 
+    update(target: result, with: component)
+
     return result
   }
 
   public func update(
     target: TestView,
     with component: TestRenderer.MountedHost
-  ) {}
+  ) {
+    guard
+      let componentType = component.type as? AnyRefComponent.Type,
+      let anyRef = component.node.ref else { return }
+
+    componentType.update(ref: anyRef, with: target)
+  }
 
   public func unmount(
     target: TestView,

Tests/TokamakTests/HooksTests.swift

@@ -10,6 +10,10 @@ import XCTest
 
 @testable import Tokamak
 
+extension Button: RefComponent {
+  public typealias RefTarget = TestView
+}
+
 extension Int: Updatable {
   public enum Action {
     case increment
@@ -39,10 +43,14 @@ struct Test: LeafComponent {
     let state1 = hooks.custom()
     let state2 = hooks.custom()
     let state3 = hooks.custom()
+    let ref = hooks.ref(type: TestView.self)
 
     return StackView.node([
-      Button.node(.init(onPress: Handler { state1.set { $0 += 1 } }),
-                  "Increment"),
+      Button.node(
+        ref: ref,
+        .init(onPress: Handler { state1.set { $0 += 1 } }),
+        "Increment"
+      ),
       Label.node("\(state1.value)"),
       Button.node(.init(onPress: Handler { state2.set { $0 + 1 } }),
                   "Increment"),
@@ -67,12 +75,15 @@ final class HooksTests: XCTestCase {
       let button2Props = stack.subviews[2].props(Button.Props.self),
       let button2Handler = button2Props.handlers[.touchUpInside]?.value,
       let button3Props = stack.subviews[4].props(Button.Props.self),
-      let button3Handler = button3Props.handlers[.touchUpInside]?.value
+      let button3Handler = button3Props.handlers[.touchUpInside]?.value,
+      let button1Ref = stack.subviews[0].node.ref as? Ref<TestView?>
     else {
       XCTAssert(false, "components have no handlers")
       return
     }
 
+    XCTAssertTrue(button1Ref.value === stack.subviews[0])
+
     button1Handler(())
 
     button2Handler(())