Re: [Firebird-devel] Reference counters in API - was Re: Providers, yvalve, external engines and object lifecycle

[Daniel R. <da...@ac...>]

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Hi,

Just to clarify a few things with relations to Delphi.

At March-30-11, 12:33 PM, Adriano dos Santos Fernandes wrote:

> On 30-03-2011 08:04, Vlad Khorsun wrote:
>> 
>>     With Delphi you will just use IAttachment, without SmartPtr, as Delphi's "interface" have
>> built-in compiler magic to work with reference counts.
>> 
> AFAIK, this is not how it works.

> Delphi "interface" has nothing directly related with refcount.

Actually, Vlad is correct.
Here's what is written in Delphi's help for IInterface:

  "IInterface introduces the QueryInterface method, which is useful
  for discovering and using other interfaces implemented by the same
  object. IInterface also introduces the reference counting methods,
  _AddRef and _Release. The Delphi compiler automatically provides
  calls to these methods when interfaces are used. The
  TInterfacedObject class is provided as a base class for objects that
  implement interfaces. Use of TInterfacedObject is not mandatory, but
  will often be easier than designing an implementer class from
  scratch."

> Refcount comes on when IInterface is used, but IInterface is about COM
> (has queryInterface). I don't think you can make our interfaces to work
> with IInterface, so you won't get RAII with Delphi and our interfaces.

You are correct when you say "Refcount comes on when IInterface is
used".  But, Delphi's IInterface has nothing to do with COM, as I can
use IInterface in an application, without ever using COM.  And, there
are some that was able to implement RAII in Delphi, with the use of
IInterface (I did a search on Google).

-- 
Best regards,
 Daniel Rail
 Senior Software Developer
 ACCRA Solutions Inc. (www.accra.ca)
 ACCRA Med Software Inc. (www.filopto.com)