fix errors

src/DataStructure/CacheItem.cs

@@ -1,17 +1,23 @@
+using System.Diagnostics;
+
 namespace Skeleton.DataStructure;
 
 /// <summary>
 ///     store value from calculation to avoid redundant computations
 /// </summary>
-public abstract class CacheItem
+public class CacheItem
 {
+
+    public CacheItem(Func<CacheItem, object> cal) => ProxyCalculator = cal;
+    
+    public static readonly CacheItem Null = new CacheItem<bool>(x => false);
     /// <summary>
     ///     if the item needs update
     /// </summary>
     public bool Expired { get; protected set; } = true;
     internal HashSet<CacheItem> References { get; set; } = new();
     internal HashSet<CacheItem> Dependencies { get; set; } = new();
-
+    private Func<object> Calculator => () => ProxyCalculator(this);
     /// <summary>
     ///     tag the item and all dependencies as out dated
     /// </summary>
@@ -22,6 +28,32 @@ public abstract class CacheItem
             if (!c.Expired)
                 c.Expire();
     }
+    
+    public TObject Get<TObject>() => (this as CacheItem<TObject>)!.Get;
+    private object? Value { get; set; }
+    public void Assign(object o) => UpdateCalculation(x => o);
+    public object Get()
+    {
+        if (Expired)
+        {
+            Value = Calculator();
+            Expired = false;
+        }
+        return Value!;
+    }
+
+    public TObject GetFrom<TObject>(CacheItem item) => (this as CacheItem<TObject>)!.GetFrom(item);
+
+    public object GetFrom(CacheItem item)
+    {
+        References.Add(item);
+        item.Dependencies.Add(this);
+        return Get();
+    }
+
+    public Func<CacheItem, object> ProxyCalculator { get; internal set; }
+
+    public void UpdateCalculation(Func<CacheItem, object> a) => ProxyCalculator = a;
 }
 
 /// <inheritdoc />
@@ -31,12 +63,15 @@ public class CacheItem<TObject> : CacheItem
     ///     construct by provide a method to update the value
     /// </summary>
     /// <param name="rec"></param>
-    public CacheItem(Func<CacheItem, TObject> rec) => ProxyCalculator = rec;
+    public CacheItem(Func<CacheItem, TObject> rec) : base(x => rec(x))
+    {
+    }
+
     private TObject? Value { get; set; }
     /// <summary>
     ///     return cached/updated value when reference is not used to calculate another cache item
     /// </summary>
-    public TObject Get
+    public new TObject Get
     {
         get
         {
@@ -49,16 +84,21 @@ public class CacheItem<TObject> : CacheItem
         }
     }
     private Func<TObject> Calculator => () => ProxyCalculator(this);
+
     /// <summary>
     /// provide trace information while calculating
     /// </summary>
-    public Func<CacheItem, TObject> ProxyCalculator { get; internal set; }
+    public new Func<CacheItem, TObject> ProxyCalculator
+    {
+        get => x => (TObject)base.ProxyCalculator(x); 
+        set => base.ProxyCalculator = x => value(x)!;
+    }
     /// <summary>
     ///     trace the dependency and return cached value/updated value
     /// </summary>
     /// <param name="d"></param>
     /// <returns></returns>
-    public TObject GetFrom(CacheItem d)
+    public new TObject GetFrom(CacheItem d)
     {
         References.Add(d);
         d.Dependencies.Add(this);
@@ -78,5 +118,7 @@ public class CacheItem<TObject> : CacheItem
     }
     
 
+    public void Assign(TObject b) => UpdateCalculation(x => b);
+
 }