Refactoring

Src/Myc.Signals.pas

@@ -21,10 +21,11 @@ type
         FState: IMycState;
         FTag: TMycNotifyList<IMycSubscriber>.TTag; // Tag identifying this subscription within the notifier list.
         function GetState: IMycState;
-        constructor Create(const AState: IMycState; ATag: TMycNotifyList<IMycSubscriber>.TTag);
     public
+        constructor Create(const AState: IMycState; ATag: TMycNotifyList<IMycSubscriber>.TTag);
         // Unsubscribes from the associated signal.
         procedure Unsubscribe;
+        class operator Initialize(out Dest: TMycSubscription);
         property State: IMycState read GetState;
     end;
 
@@ -154,44 +155,44 @@ uses
     System.SyncObjs; // For TInterlocked
 
 type
-    // TMycNullState implements a "null object" pattern for IMycState.
-    // This state is always considered "set".
-    TMycNullState = class(TInterfacedObject, IMycState)
-    protected
-        // IMycState
-        function GetIsSet: Boolean;
-        function Subscribe(const Subscriber: IMycSubscriber): TMycSubscription;
-        procedure Unsubscribe(Tag: TMycNotifyList<IMycSubscriber>.TTag);
-    public
-        constructor Create;
-    end;
-
-{ TMycNullState }
-
-constructor TMycNullState.Create;
-begin
-    inherited Create;
-end;
-
-function TMycNullState.GetIsSet: Boolean;
-begin
-    Result := true; // Null state is always set.
-end;
-
-function TMycNullState.Subscribe(const Subscriber: IMycSubscriber): TMycSubscription;
-begin
-    // Since the state is always set, notify the subscriber immediately.
-    if Assigned(Subscriber) then
-    begin
-        Subscriber.Notify;
-    end;
-    // No ongoing subscription is necessary or meaningful for a null state.
-    Result.Create(Self, nil); // Return an empty subscription.
-end;
-
-procedure TMycNullState.Unsubscribe(Tag: TMycNotifyList<IMycSubscriber>.TTag);
-begin
-    // Unsubscribing from a null state has no effect.
+    // TMycNullState implements a "null object" pattern for IMycState.
+    // This state is always considered "set".
+    TMycNullState = class(TInterfacedObject, IMycState)
+    protected
+        // IMycState
+        function GetIsSet: Boolean;
+        function Subscribe(const Subscriber: IMycSubscriber): TMycSubscription;
+        procedure Unsubscribe(Tag: TMycNotifyList<IMycSubscriber>.TTag);
+    public
+        constructor Create;
+    end;
+
+{ TMycNullState }
+
+constructor TMycNullState.Create;
+begin
+    inherited Create;
+end;
+
+function TMycNullState.GetIsSet: Boolean;
+begin
+    Result := true; // Null state is always set.
+end;
+
+function TMycNullState.Subscribe(const Subscriber: IMycSubscriber): TMycSubscription;
+begin
+    // Since the state is always set, notify the subscriber immediately.
+    if Assigned(Subscriber) then
+    begin
+        Subscriber.Notify;
+    end;
+    // No ongoing subscription is necessary or meaningful for a null state.
+    Result.Create(Self, nil); // Return an empty subscription.
+end;
+
+procedure TMycNullState.Unsubscribe(Tag: TMycNotifyList<IMycSubscriber>.TTag);
+begin
+    // Unsubscribing from a null state has no effect.
 end;
 
 { TMycSubscription }
@@ -206,17 +207,20 @@ end;
 
 procedure TMycSubscription.Unsubscribe;
 begin
-    if Assigned(FState) then
-    begin
-        FState.Unsubscribe(FTag);
-        FTag := nil;
-        FState := nil;
-    end;
+    FState.Unsubscribe(FTag);
+    FState := TMycState.Null;
+    FTag := nil;
 end;
 
 function TMycSubscription.GetState: IMycState;
 begin
-    Result := FState;
+    Result := FState
+end;
+
+class operator TMycSubscription.Initialize(out Dest: TMycSubscription);
+begin
+    Dest.FState := TMycState.Null;
+    Dest.FTag := nil;
 end;
 
 { TMycLatch }
@@ -301,7 +305,6 @@ function TMycLatch.Subscribe(const Subscriber: IMycSubscriber): TMycSubscription
 var
     alreadySet: Boolean;
 begin
-    Result.Create(TMycState.Null, nil); // Default to an empty subscription.
     if not Assigned(Subscriber) then
         exit;
 
@@ -409,7 +412,6 @@ end;
 
 function TMycDirty.Subscribe(const Subscriber: IMycSubscriber): TMycSubscription;
 begin
-    Result.Create(TMycState.Null, nil); // Default to an empty subscription
     if not Assigned(Subscriber) then
         exit;