[DUG] Returning a WideString in an Invoke Param

[Phil Middlemiss]

I have avoided that one because if I set pbstrVal^ then I'm writing 
directly into memory which should just end up causing an access violation.

Todd Martin wrote:
> Okay. How about setting the "value" of the widestring pointer.
>
> Parameters.rgvarg[1].pbstrVal^ := layermanagerid;
>
> ----- Original Message ----- From: "Phil Middlemiss" <phil at tumonz.co.nz>
> To: "NZ Borland Developers Group - Delphi List" <delphi at ns3.123.co.nz>
> Sent: Tuesday, July 18, 2006 12:30 PM
> Subject: Re: [DUG] Returning a WideString in an Invoke Param
>
>
>> Yes, I checked after my initial post, and it is a pbstrVal.
>>
>> I can read the value fine. It's writing the value that seems to be the
>> problem. The Params parameter is a Var parameter so that you can return
>> values in it if you need to. I tried just pointing the pbstrVal to a new
>> WideString, but it still ends up an empty string by the time it gets
>> back to the automation server, so
>>
>>        Parameters.rgvarg[1].pbstrVal := @layermanagerid;
>> //layermangerid is a WideString
>>
>> doesn't work. I think, as Conor says, I need to construct an OleVariant
>> to return, but the Parameters.rgvarg[1] still needs to be a pbstrVal.
>> Not quite sure how to fit the bits together.
>>
>> Phil.
>>
>> Todd Martin wrote:
>>> Have you checked the TVarType of parameter 1? Is it actually a bStrVal
>>> and not pbstrVal?
>>>
>>> For pbstrVal just dereference the pointer to an ordinary string
>>> variable. The conversion is automatic.
>>>
>>> var
>>>  myValue : string;
>>> begin
>>>   myValue := Params.rgvarg[1].pbstrVal^;
>>> end;
>>>
>>>
>>> ----- Original Message ----- From: "Phil Middlemiss" 
>>> <phil at tumonz.co.nz>
>>> To: "NZ Borland Developers Group - Delphi List" <delphi at ns3.123.co.nz>
>>> Sent: Tuesday, July 18, 2006 11:13 AM
>>> Subject: [DUG] Returning a WideString in an Invoke Param
>>>
>>>
>>>> Hi all,
>>>>
>>>> I have an automation object with events. One of the events has a 
>>>> couple
>>>> of VAR parameters which I'm not quite sure how to handle. Here is the
>>>> code that is NOT working:
>>>>
>>>> procedure TT3SDKEvents.DoInvoke(Sender : TObject; DispID: Integer; 
>>>> const
>>>> IID: TGUID;
>>>>  LocaleID: Integer; Flags: Word; var Params: TDispParams; VarResult,
>>>> ExcepInfo,
>>>>  ArgErr: Pointer);
>>>>    case DispID of
>>>>
>>>>    ...
>>>>
>>>>    4: { OnIdentify }
>>>>      if assigned(FOnIdentify) then
>>>>        begin
>>>>        //initialise the values
>>>>        layermanagerid :=  WideCharToString(Params.rgvarg[1].bStrVal);
>>>>        appname := WideCharToString(Params.rgvarg[0].bstrVal);
>>>>        if assigned(FOnIdentify) then
>>>>          FOnIdentify(layermanagerid, appname);
>>>>        Params.rgvarg[1].bstrVal := PWideChar(layermanagerid);
>>>>        Params.rgvarg[0].bstrVal := PWideChar(appname);
>>>>        end;
>>>>    end;
>>>> end;
>>>>
>>>> The above code just ends up returning an empty string - I've 
>>>> checked to
>>>> make sure that the call to FOnIdentify is indeed returning values.
>>>> So the question is: how should I be returning a widestring in the
>>>> TDispParams?
>>>>
>>>> Cheers,
>>>> Phil.
>>>>
>>>
>>>
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>>
>
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