lowlevel
asked on
COM server instancing
Consider an application X that uses interfaces iA and iB.
iA and iB are implemented by txA and txB, which are tAutoObject descendants.
Suppose iB stores some configuration information, and iA implements some functionality that needs the config info from iB.
A problem arises when iA's client (X) wants to touch the config-info aswell, since both X and iA need *the same* reference to iB. (I think!)
In the unit that implements txA, i have the following line:
tAutoObjectFactory.Create(
However, after digging into the VCL sourcecode, it seems that the ciSingleInstance parameter is never used again. It is only stored in the classfactory as a private variable.
Given the above scenario, i do NOT get the same references to iB in iA and X.
I've thought of creating a dll-global variable that gets set in txB.initialize if it is nil.. But how do I tell the second instance of iB to abort it's own initialization and use the dll-global variable instead?
And even then, it does not solve my original problem (X and iA using iB) when X and iA are in different address spaces. That is not a practical situation yet, but I can see it becoming one :(
Got any help?
iA and iB are implemented by txA and txB, which are tAutoObject descendants.
Suppose iB stores some configuration information, and iA implements some functionality that needs the config info from iB.
A problem arises when iA's client (X) wants to touch the config-info aswell, since both X and iA need *the same* reference to iB. (I think!)
In the unit that implements txA, i have the following line:
tAutoObjectFactory.Create(
However, after digging into the VCL sourcecode, it seems that the ciSingleInstance parameter is never used again. It is only stored in the classfactory as a private variable.
Given the above scenario, i do NOT get the same references to iB in iA and X.
I've thought of creating a dll-global variable that gets set in txB.initialize if it is nil.. But how do I tell the second instance of iB to abort it's own initialization and use the dll-global variable instead?
And even then, it does not solve my original problem (X and iA using iB) when X and iA are in different address spaces. That is not a practical situation yet, but I can see it becoming one :(
Got any help?
Have you tried ciMultiInstance???? That is it I believe, at least thats what help says.
ASKER
Nope, it ain't.
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ASKER
Works like a dream :)
Would you also happen to know why i cannot do something like
var dispatch : variant;
een : iEen;
begin
try
dispatch:=getActiveOLEObje
except
end;
if varType(dispatch)<>varDisp
then een:=coEen.create
else een:=iEen(getActiveOLEObje
end;
this will compile, it'll even run, but the iEen pointer is invalid and thus causes access violations.
I'd like to be able to convert it to a specific interface type because I like the type-checking that delphi does pre-compiling.
Would you also happen to know why i cannot do something like
var dispatch : variant;
een : iEen;
begin
try
dispatch:=getActiveOLEObje
except
end;
if varType(dispatch)<>varDisp
then een:=coEen.create
else een:=iEen(getActiveOLEObje
end;
this will compile, it'll even run, but the iEen pointer is invalid and thus causes access violations.
I'd like to be able to convert it to a specific interface type because I like the type-checking that delphi does pre-compiling.
You cannot typecast a Variant referencing an automation server directly to an interface type.
To work with interfaces rather than variants, you can do something like the following:
Try
een:=GetActiveOleObject(<Y
Except
On e:EOleError Do
een:=CoEen.Create;
End;
The trick here is that the As operator will do the appropriate conversion to your interface type.
I hope this is what you ment.
Regards,
AndersWP
To work with interfaces rather than variants, you can do something like the following:
Try
een:=GetActiveOleObject(<Y
Except
On e:EOleError Do
een:=CoEen.Create;
End;
The trick here is that the As operator will do the appropriate conversion to your interface type.
I hope this is what you ment.
Regards,
AndersWP
ASKER
yup, thanx :)