[fpc-pascal] Re: JSON & me - blind again?

[Michael Van Canneyt]

On Tue, 12 Mar 2013, Reinier Olislagers wrote:

> On 12-3-2013 11:44, Michael Van Canneyt wrote:
>
> Thanks for the help, Michael.
>
>> On Tue, 12 Mar 2013, Reinier Olislagers wrote:
>>> //===> the line below works - so CommJSON is a valid object, right?
>>>        if Assigned(CommJSON) then
>>
>> It is assigned, but not necessarily valid. If you freed CommJSON but did
>> not nil it, it is still'assigned'.
> Understood. Then it has a pointer pointing to whatever (probably the
> object's former memory location).
>
>>> I'm not confident about
>>> function HttpRequestWithData(AData: TJSONData; const AUrl: string;
>>>  const AMethod: TRequestMethod; const AContentType: string): THttpResult;
>>
>> Ehm. This must be
>>
>>  function HttpRequestWithData(OUT AData: TJSONData; const AUrl: string;
>>   const AMethod: TRequestMethod; const AContentType: string): THttpResult;
>>
>> Because you are passing BACK a reference!
>
> Sorry. What I hadn't attached is the first part where the request is
> built up:
>    if Assigned(AData) then
>    begin
>      VHttp.RequestBody := TMemoryStream.Create;
>      VJSON := AData.AsJSON;
>      VHttp.RequestBody.Write(Pointer(VJSON)^, Length(VJSON));
>      VHttp.RequestBody.Position := 0;
>    end;

Yes, but as per your code: you free and rebuild:

       FreeAndNil(AData);
       VData.Position := 0;

-> so you change the parameter, and thus you need a var/out

Anyway, glad it is fixed.

Michael.