Does reference counting still works with Delphi Interfaces when you don't provide a guid?

Question

I have the following interface:

type IDataAccessObject<Pk; T:class> = interface
   getByPrimaryKey(key: PK) : T;
   //... more methods
end;

And an implementation of the interface as follows:

type TMyClassDAO = class(TInterfacedObject, IDataAccessObject<integer, TMyClass>)
   getByPrimaryKey(key:integer) : TMyClass;
   // more methods
end;

Note that I am not providing a guid for the interface (because every instantiation of the previous generic interface is a different interface and they should not share the same guid). However I am not sure whether that does not break reference counting implemented by TInterfacedObject?

See also [Are GUIDs necessary to use interfaces in Delphi?](https://stackoverflow.com/q/2992183/576719). — LU RD, May 25 '17 at 13:33

score 15 · Accepted Answer · edited May 25 '17 at 16:21

15

Reference counting does not rely on a GUID, but on _AddRef() and _Release() method implementations.

Since you inherit from TInterfacedObject, reference counting will work for all of your object instances.

The only thing you lose if you don't provide a GUID is the ability to query one interface from another, such as in calls to the Supports() function, QueryInterface() interface method, and the is and as operators.

edited May 25 '17 at 16:21

Remy Lebeau

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answered May 25 '17 at 11:14

Dalija Prasnikar

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Thanks for the clarifications! – BigONotation May 25 '17 at 11:23

Does reference counting still works with Delphi Interfaces when you don't provide a guid?

1 Answers1