CORBA interface and Variants
lazarus / 62-General

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JdeHaan · 2024-04-16 10:51

Hi,

For various reasons I use CORBA interfaces. In my code I also use
Variants, to support different types of value in a variable. This may
include an interface value.

At some point I need to check if a Variable (of type Variant) is a
(CORBA) interface. I use the following code for that:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
isSymTabEntry := VarSupports(Value, StringToGUID(ISymTabEntry_GUID),
SymTabEntry); Here, Value is a variable of type Variant,
ISymTabEntry_GUID, is a string constant, such as:
'{DCD95BA9-90CB-9AA2-0090-DBA0749AF179}'
and SymTabEntry is a CORBA interface ISymTabEntry, defined as :

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  
ISymTabEntry = interface    [ISymTabEntry_GUID]    function getName:
String;    //etc…  end; It doesn’t seem to work. Function getName
produces the GUID string constant instead of the name of the
SymTabEntry…
Could it be that only COM interfaces can be used with VarSupports?

Is there maybe another way of retrieving an Interface value/variable
from a Variant value?

Any suggestion is appreciated.

Regards, J



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I use trunk Lazarus and FPC on MacOS Sonoma

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cdbc · 2024-04-16 12:17

Hi
Have you tried:Code: Pascal  [Select][+][-]window.onload =
function(){var x1 = document.getElementById("main_content_section");
if (x1) { var x = document.getElementsByClassName("geshi");for (var i
= 0; i S:= SymTabEntry.GetName(); // NOTE the () Funny thing about
corba-interfaces: *they typecast to string* i.e.: the string
representation of the guid.
So given your method returns a string, if you don't add the
parantheses / braces, it doesn't count that as a method-call and
returns the string-rep. of the interface... At least that's my
experience so far...
Regards Benny

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marcov · 2024-04-16 13:11

Afaik the methods to query nearly everything from an interface are in
iunknown (the com base interface).

So yeah, probably that won't work.

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JdeHaan · 2024-04-16 14:06

Ok, thanks.

@cdbc, I tried but unfortunately I get the same result...

Edit:
Just found out that the VarSupports never returns TRUE, so this is not
working

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Thaddy · 2024-04-16 14:27

Quote from: JdeHaan on April 16, 2024, 12:51:37 pmFor various reasons
I use CORBA interfaces.
Bad habit. Give me one various reason. Then I might be able to help.

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JdeHaan · 2024-04-16 14:56

I know it's not optimal to use Corba interfaces.
But, the problem I was facing was that in order to use a COM
interface, my class definition had to inherit from TInterfacedObject,
but I also had to inherit from another class. To prevent that I used
Corba.
I'm now thinking of creating my own value type, based on a variant
record instead of a Variant type. So, basically:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type  
TMyRec = record    case byte of     0: (IntVal: Integer);     1:
(FloatVal: Real);     2: (IntfVal: IMyCorbaInterface);  end;

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PascalDragon · 2024-04-16 18:35

Quote from: JdeHaan on April 16, 2024, 04:56:48 pmBut, the problem I
was facing was that in order to use a COM interface, my class
definition had to inherit from TInterfacedObject, but I also had to
inherit from another class. To prevent that I used Corba.
You don't have to inherit from TInterfacedObject, but what you have to
do is to implement the methods of IInterface/IUnknown (which is what
TInterfacedObject does).