Implementing Unary Operations

Go Up to Creating a Class to Enable the Custom Variant Type

To allow the custom variant type to work with standard unary operators ( -, not), you must override the UnaryOp method. UnaryOp has two parameters: the value of the operand and the operator. Implement this method to perform the operation and return the result using the same variable that contained the operand.

 procedure TComplexVariantType.UnaryOp(var Right: TVarData; const Operator: TVarOp);
 begin
 if Right.VType = VarType then
 case Operator of
 opNegate:
 TComplexVarData(Right).VComplex.DoNegate;
 else
 RaiseInvalidOp;
 end
 else
 RaiseInvalidOp;
 end;

Note that for the logical not operator, which does not make sense for complex values, this method calls RaiseInvalidOp to cause a runtime error.

See Also

• Implementing Binary Operations
• Implementing Comparison Operations
• Enabling Casting
• Copying and Clearing Custom Variants
• Using the TCustomVariantType Descendant
• Loading and Saving Custom Variant Values

• Windows Developer's Guide
• Delphi

• AMMigrate