Only save the two most recent state identifiers

Sources/Model/Data Flow/StateManager.swift

@@ -23,12 +23,26 @@ public enum StateManager {
     struct State {
 
         /// The state's identifiers.
-        var ids: [UUID]
+        var ids: (first: UUID, second: UUID?)
         /// The state value.
         var value: Any?
         /// Whether to update in the next iteration.
         var update = false
 
+        /// Whether the state's identifiers contain a certain identifier.
+        /// - Parameter id: The identifier.
+        /// - Returns: Whether the id is contained.
+        func contains(id: UUID) -> Bool {
+            ids.first == id || ids.second == id
+        }
+        
+        /// Change the identifier to a new one.
+        /// - Parameter newID: The new identifier.
+        mutating func changeID(new newID: UUID) {
+            ids.second = ids.first
+            ids.first = newID
+        }
+
     }
 
     /// Update all of the views.
@@ -55,8 +69,8 @@ public enum StateManager {
     ///   - value: The new value.
     static func setState(id: UUID, value: Any?) {
         if saveState {
-            guard let index = state.firstIndex(where: { $0.ids.contains(id) }) else {
-                state.append(.init(ids: [id], value: value))
+            guard let index = state.firstIndex(where: { $0.contains(id: id) }) else {
+                state.append(.init(ids: (first: id, second: nil), value: value))
                 return
             }
             state[safe: index]?.value = value
@@ -67,14 +81,14 @@ public enum StateManager {
     /// - Parameter id: The identifier.
     /// - Returns: The value.
     static func getState(id: UUID) -> Any? {
-        state[safe: state.firstIndex { $0.ids.contains(id) }]?.value
+        state[safe: state.firstIndex { $0.contains(id: id) }]?.value
     }
 
     /// Mark the state of a certain id as updated.
     /// - Parameter id: The identifier.
     static func updateState(id: UUID) {
         if saveState {
-            state[safe: state.firstIndex { $0.ids.contains(id) }]?.update = true
+            state[safe: state.firstIndex { $0.contains(id: id) }]?.update = true
         }
     }
 
@@ -82,7 +96,7 @@ public enum StateManager {
     /// - Parameter id: The identifier.
     static func updatedState(id: UUID) {
         if saveState {
-            state[safe: state.firstIndex { $0.ids.contains(id) }]?.update = false
+            state[safe: state.firstIndex { $0.contains(id: id) }]?.update = false
         }
     }
 
@@ -90,7 +104,7 @@ public enum StateManager {
     /// - Parameter id: The identifier.
     /// - Returns: Whether to update the state.
     static func getUpdateState(id: UUID) -> Bool {
-        state[safe: state.firstIndex { $0.ids.contains(id) }]?.update ?? false
+        state[safe: state.firstIndex { $0.contains(id: id) }]?.update ?? false
     }
 
     /// Change the identifier for a certain state value.
@@ -99,7 +113,7 @@ public enum StateManager {
     ///   - newID: The new identifier.
     static func changeID(old oldID: UUID, new newID: UUID) {
         if saveState {
-            state[safe: state.firstIndex { $0.ids.contains(oldID) }]?.ids.append(newID)
+            state[safe: state.firstIndex { $0.contains(id: oldID) }]?.changeID(new: newID)
         }
     }
 

Tests/DemoApp/DemoApp.swift

@@ -7,12 +7,12 @@ import SampleBackends
 @available(iOS 17, *)
 struct DemoView: View {
 
-    @State private var test = TestModel()
+    @State private var model = TestModel()
 
     var view: Body {
         Backend1.TestWidget1()
-        Backend1.Button(test.test) {
-            test.test = "\(Int.random(in: 1...10))"
+        Backend1.Button(model.test) {
+            model.test = "\(Int.random(in: 1...10))"
         }
         TestView()
         testContent
@@ -66,6 +66,7 @@ struct DemoApp {
         }
 
         StateManager.addUpdateHandler { force in
+            print("#*")
             DemoView().updateStorage(storage, modifiers: [], updateProperties: force, type: backendType)
         }
 

Tests/SampleBackends/Backend1.swift

@@ -3,9 +3,9 @@ import Meta
 public enum Backend1 {
 
     public struct TestWidget1: BackendWidget {
-    
+
         public init() { }
-    
+
         public func container<WidgetType>(modifiers: [(AnyView) -> AnyView], type: WidgetType.Type) -> ViewStorage {
             print("Init test widget 1")
             let storage = ViewStorage(nil)
@@ -17,9 +17,9 @@ public enum Backend1 {
             print("Update test widget 1 (#\(storage.fields["test"] ?? ""))")
             storage.fields["test"] = (storage.fields["test"] as? Int ?? 0) + 1
         }
-    
+
     }
-    
+
     public struct TestWidget3: BackendWidget {
 
         public init() { }
@@ -50,16 +50,19 @@ public enum Backend1 {
 
         public func container<WidgetType>(modifiers: [(any AnyView) -> any AnyView], type: WidgetType.Type) -> ViewStorage {
             print("Init button")
+            let storage = ViewStorage(nil)
             Task {
                 try await Task.sleep(nanoseconds: 1_000_000_000)
-                action()
+                (storage.fields["action"] as? () -> Void)?()
             }
-            return .init(nil)
+            storage.fields["action"] = action
+            return storage
         }
 
         public func update<WidgetType>(_ storage: ViewStorage, modifiers: [(any AnyView) -> any AnyView], updateProperties: Bool, type: WidgetType.Type) {
             if updateProperties {
                 print("Update button (label = \(label))")
+                storage.fields["action"] = action
             } else {
                 print("Do not update button (label = \(label))")
             }
@@ -70,3 +73,4 @@ public enum Backend1 {
     public protocol BackendWidget: Widget { }
 
 }
+