TCustomVariantType is the base class for Delphi custom variant types.
Use TCustomVariantType to define new data types for Delphi Variants. TCustomVariantType descendants do not represent the Variants themselves. Rather, they act as utility classes that the custom Variants call on to perform their operations.
To create a System::Variant type,
3.Declare a class that descends from TCustomVariantType.
4.Implement all required behavior (including type conversion rules) in the new class. This involves overriding the appropriate virtual methods (typically BinaryOp, UnaryOp, CompareOp or Compare, Cast, CastTo, Clear, Copy, IsClear, LeftPromotion, and RightPromotion).
5.In the initialization section of the unit that defines your TCustomVariantType descendant, create an instance of your class. When you instantiate your object, it automatically registers itself with the System::Variant-handling system so that the new System::Variant type is enabled.
6.In the finalization section of the unit that defines your TCustomVariantType descendant, free the instance of your class. This automatically unregisters the System::Variant type.
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