Refactor StepWrapper and introduce StepSystem for observer pattern. Remove unused StepSteps struct and update MutateID method. Enhance StepsMacro to notify observers on selection changes.</message>

Author: dankinsoid

Sources/VDFlow/MutateID.swift

@@ -15,7 +15,7 @@ public struct MutateID: Comparable, Hashable, Codable, Sendable {
 		try (mutationDate ?? 0).encode(to: encoder)
 	}
 
-	public mutating func _update() {
+	mutating func update() {
 		mutationDate = DispatchTime.now().uptimeNanoseconds
 	}
 

Sources/VDFlow/StepSystem.swift

@@ -0,0 +1,25 @@
+import Foundation
+
+public protocol StepsObserver: Sendable {
+
+	func stepWillChange<Parent: StepsCollection, Value>(to newValue: Parent.AllSteps, in type: Parent.Type, with value: Value)
+    func stepDidChange<Parent: StepsCollection, Value>(to newValue: Parent.AllSteps, in type: Parent.Type, with value: Value)
+}
+
+public struct NoopStepsObserver: StepsObserver {
+
+    public init() {}
+
+    public func stepWillChange<Parent: StepsCollection, Value>(to newValue: Parent.AllSteps, in type: Parent.Type, with value: Value) {}
+	public func stepDidChange<Parent: StepsCollection, Value>(to newValue: Parent.AllSteps, in type: Parent.Type, with value: Value) {}
+}
+
+public enum StepSystem {
+
+	public static var observer: StepsObserver {
+		get { lock.withLock { _observer } }
+		set { lock.withLock { _observer = newValue } }
+	}
+	private static let lock = NSRecursiveLock()
+	private static var _observer: StepsObserver = NoopStepsObserver()
+}

Sources/VDFlow/StepWrapper.swift

@@ -5,11 +5,16 @@ public extension StepsCollection {
 	typealias StepID<Value> = VDFlow.StepWrapper<Self, Value>
 }
 
+public protocol StepWrapperType {
+
+	mutating func select()
+}
+
 @propertyWrapper
-public struct StepWrapper<Parent: StepsCollection, Value>: Identifiable {
+public struct StepWrapper<Parent: StepsCollection, Value>: Identifiable, StepWrapperType {
 
 	public let id: Parent.AllSteps
-	public var _mutateID = MutateID()
+	private var mutateID = MutateID()
 	public var wrappedValue: Value
 	public var projectedValue: StepWrapper {
 		get { self }
@@ -25,7 +30,9 @@ public struct StepWrapper<Parent: StepsCollection, Value>: Identifiable {
 	}
 
 	public mutating func select() {
-		_mutateID._update()
+        StepSystem.observer.stepWillChange(to: id, in: Parent.self, with: wrappedValue)
+		mutateID.update()
+		StepSystem.observer.stepDidChange(to: id, in: Parent.self, with: wrappedValue)
 	}
 
 	public mutating func select(with value: Value) {
@@ -35,7 +42,7 @@ public struct StepWrapper<Parent: StepsCollection, Value>: Identifiable {
 
 	public var _lastMutateID: (Parent.AllSteps, MutateID)? {
         let lastNested = (wrappedValue as? any StepsCollection)?._lastMutateID?.optional
-        let this = _mutateID.optional
+        let this = mutateID.optional
         return [lastNested, this]
             .compactMap { $0 }
             .sorted { $0 > $1 }

Sources/VDFlow/macros.swift

@@ -9,13 +9,3 @@ public macro Steps() = #externalMacro(module: "VDFlowMacros", type: "StepsMacro"
 @attached(accessor, names: named(didSet))
 public macro Step() = #externalMacro(module: "VDFlowMacros", type: "StepsMacro")
 #endif
-
-@Steps
-public struct StepSteps {
-
-    public var value: Int = SomeInt()
-    public var int = Int()
-    public var none
-}
-
-public func SomeInt() -> Int { 0 }

Sources/VDFlowMacros/StepsMacro.swift

@@ -100,7 +100,11 @@ public struct StepsMacro: MemberAttributeMacro, ExtensionMacro, MemberMacro, Acc
 
 			public var selected: Self {
 			    get { self }
-			    set { self = newValue }
+			    set { 
+				   StepSystem.observer.stepWillChange(to: newValue, in: Self.self, with: ())
+			       self = newValue 
+			       StepSystem.observer.stepDidChange(to: newValue, in: Self.self, with: ())
+			    }
 			}
 			"""]
 		}
@@ -315,22 +319,23 @@ public struct StepsMacro: MemberAttributeMacro, ExtensionMacro, MemberMacro, Acc
 			public var selected: \(raw: stepsType) {
 			    get { if let result = lastMutateStepID { return result.0 } else { return \(raw: defaultValue) } }
 			    set {
-			        guard let keyPath = Self._mutateIDs[newValue] else {
+			        guard let selection = Self._selections[newValue] else {
 			            \(raw: hasDeselected ? "_deselectedMutateID._update()" : "")
 			            return
 			        }
-			        self[keyPath: keyPath]._update()
+				    selection(&self)
 			    }
 			}
 			"""
 		result.append(selected)
 
         let isSelected: DeclSyntax =
             """
-            public static func isSelected<T>(_ keyPath: WritableKeyPath<Self, StepID<T>>) -> Bool {
+            public func isSelected<T>(_ keyPath: WritableKeyPath<Self, StepID<T>>) -> Bool {
                 selected == self[keyPath: keyPath].id
             }
             """
+		result.append(isSelected)
 
 		let typealiasDecl: DeclSyntax = "public typealias AllSteps = \(raw: stepsType)"
 		result.append(typealiasDecl)
@@ -345,8 +350,8 @@ public struct StepsMacro: MemberAttributeMacro, ExtensionMacro, MemberMacro, Acc
 
 		let mutateIDs: DeclSyntax =
 			"""
-			private static var _mutateIDs: [AllSteps: WritableKeyPath<Self, MutateID>] {
-			    [\(raw: cases.map { ".\($0): \\.$\($0)._mutateID" }.joined(separator: ", "))]
+			private static var _selections: [AllSteps: (inout Self) -> Void] {
+			    [\(raw: cases.map { ".\($0): { $0.$\($0).select() }" }.joined(separator: ", "))]
 			}
 			"""
 		result.append(mutateIDs)