New type system

Src/Data/Myc.Data.Types.Decimal.pas

@@ -10,9 +10,19 @@ type
     TImplDataDecimalType = class(TInterfacedObject, IDataDecimalType)
     private
         FScale: Integer;
+    strict private
+        class var
+            // Pre-cached instances for scales 0-18.
+            FDecimalTypes: TArray<IDataDecimalType>;
     public
         constructor Create(const AScale: Integer);
 
+        class constructor CreateClass;
+        class destructor DestroyClass;
+
+        // Returns a cached instance for the specified scale.
+        class function GetInstance(const AScale: Integer): IDataDecimalType; static;
+
         // IDataType
         function GetName: String;
         function GetKind: TDataKind;
@@ -54,6 +64,28 @@ begin
     FScale := AScale;
 end;
 
+class constructor TImplDataDecimalType.CreateClass;
+var
+    i: Integer;
+begin
+    // Create and cache singleton instances for each supported scale.
+    SetLength(FDecimalTypes, 19);
+    for i := 0 to High(FDecimalTypes) do
+        FDecimalTypes[i] := TImplDataDecimalType.Create(i);
+end;
+
+class destructor TImplDataDecimalType.DestroyClass;
+begin
+    FDecimalTypes := nil;
+end;
+
+class function TImplDataDecimalType.GetInstance(const AScale: Integer): IDataDecimalType;
+begin
+    if (AScale < 0) or (AScale > High(FDecimalTypes)) then
+        raise EArgumentException.CreateFmt('Scale for decimal must be between 0 and %d.', [High(FDecimalTypes)]);
+    Result := FDecimalTypes[AScale];
+end;
+
 function TImplDataDecimalType.CreateValue(const AValue: Int64): IDataDecimalValue;
 begin
     Result := TDataDecimalValue.Create(AValue, Self);