[omniORB] Can't compile client that retrieves a struct which contains a sequence

[Luke Deller]

Hi Tom,

> void foo(SequenceTestIF_var seqTest) {
>
>   SequenceTestIF::Message msg;
>
>   seqTest->setMessage(msg);   // compiles OK
>
>   seqTest->getMessage(msg);   // Does not compile!
> }
...
> Looking at the generated IDL header file, getMessage() is defined as
> follows:
> virtual void getMessage(SequenceTestIF::Message_out msg) = 0;
> So it appears that the compiler is expecting the getMessage() parameter
> to be of type "SequenceTestIF::Message_out".  So I modified the client:
>
>   SequenceTestIF::Message_out msgOut;
>   seqTest->getMessage(msgOut);   // Still does not compile!

Not quite... here's a quote from section 4.11.2 of the C++ language mapping:

| Note that the T_out types are not intended to serve as general-purpose
| data types to be created and destroyed by applications; they are used
| only as types within operation signatures to allow necessary memory
| management side-effects to occur properly.

So you don't actually construct a Message_out instance explicitly.  Basically you want to pass a reference to a pointer, so that the function can point your pointer at the returned message:

    SequenceTestIF::Message *msgptr;
    seqTest->getMessage(msgptr);
    // now you can use msgptr->body
    seqTest->setMessage(*msgptr);
    delete msgptr;

Alternatively you can use the Message_var type to ease memory management:

    SequenceTestIF::Message_var msg;
    seqTest->getMessage(msg);
    // now you can use msg->body
    seqTest->setMessage(msg);
    // no need to delete anything; the Message_var destructor handles it

For more details, check out the IDL C++ language mapping which is available for download from:
http://www.omg.org/technology/documents/idl2x_spec_catalog.htm

Regards,
Luke.
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