JVCL Help:TExtensibleInterfacedPersistent
JVCL Help: TExtensibleInterfacedPersistent Class
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TExtensibleInterfacedPersistent
TJvBaseDataContext
TJvBaseDataContexts
TJvBaseDataItem
TJvBaseDataItems
TJvDataConsumer
run\JvDataProvider.pas
Summary
Ancestor for persistent objects that implement interfaces and can be extended at run time.
Pascal
run\JvDataProvider.pas
TExtensibleInterfacedPersistent = class(TPersistent, IUnknown);
Description
TExtensibleInterfacedPersistent, like its ancestor, provides functionality to read and write its to and from a stream. In addition, like the Delphi provided TInterfacedPersistent, it also supplies a default implementation for the IInterface methods.
Furthermore, TExtensibleInterfacedPersistent allows itself to be extended through aggregators, where the interfaced supported by those aggregators are directly accessible from the main object, as well as from each other. The aggregators must be derived from TAggregatedPersistentEx for this behavior to work correctly. In addition, TExtensibleInterfacedPersistent automatically provides semi properties that allow the extensions to be read and written from and to a stream.
This extensibility is achieved by having the QueryInterface method of IInterface call the redeclared and virtual GetInterface method. This method will simply call the Delphi provided implementation and if a match is not found, the aggregators (called "extensions" in this context) are iterated until an extension is found that supports the interface. The first match is returned (this implies that if multiple extension happen to share a common interface, only the first added extension will be returned).
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