Custom variants work by using a special helper class that indicates how variants of the custom type can perform standard operations. You create this helper class by writing a descendant of TCustomVariantType. This involves overriding the appropriate virtual methods of TCustomVariantType. 

The following topics provide details on how to implement and use a TCustomVariantType descendant:

• Enabling casting
• Implementing binary operations
• Implementing comparison operations
• Implementing unary operations
• Copying and clearing custom variants
• Loading and saving custom variant values
• Using the TCustomVariantType descendant