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[cellml-dev] CellML wchar sizes


Chronological Thread 
  • From: ak.miller at auckland.ac.nz (Andrew Miller)
  • Subject: [cellml-dev] CellML wchar sizes
  • Date: Fri, 04 Dec 2009 13:07:52 +1300
Lucian Smith wrote:
> Ok, I appear to be taking things in tiny tiny baby steps, but I keep
> thinking that if only I understood the next bit, I'd get it. If we take a
> slightly-modified version of your code:
>
> nsresult rv;
> nsCOMPtr<cellml_apiICellMLBootstrap>
> boot(do_GetService(CELLML_BOOTSTRAP_CONTRACTID, &rv));
> NS_ENSURE_SUCCESS(rv, );
> nsCOMPtr<cellml_apiIModel> mod;
> rv = boot->CreateModel(NS_LITERAL_STRING("1.1"), getter_AddRefs(mod));
> NS_ENSURE_SUCCESS(rv, );
>
> (NS_ENSURE_SUCCESS(rv, rv) didn't compile for some reason; I saw the above
> version in DataCollector.cpp so I went with that and it compiled. I don't
> know why, but I'm not complaining...)

That's probably because the function you were in doesn't return nsresult.

NS_ENSURE_SUCCESS(a, b) checks if a is a successful code (e.g. NS_OK is
an example of a successful code, while NS_ERROR_FAILURE is an example of
a failure code). If it is a failure code, it returns b.

All XPCOM methods return nsresult, but if you are calling XPCOM from a
non-XPCOM method you need to adjust the NS_ENSURE_SUCCESS second
parameter to return an appropriate thing (in your case, not returning
anything because presumably you are in a void method).

>
> To me, it seemed like since you created 'boot' using those methods, and
> then called a function that was originally defined for the CellML
> Bootstrap interface thingy, I could then do the following:
>
> nsCOMPtr<cellml_apiICellMLComponentSet> components =
> mod->localComponents();

That's because all XPCOM functions return nsresult, and the return value
is the second parameter. They also capitalise the first letter. So you need:

nsCOMPtr<cellml_apiICellMLComponentSet> components;
rv = mod->LocalComponents(getter_AddRefs(components));
NS_ENSURE_SUCCESS(rv, );

I'd suggest reading up on XPCOM - there is a lot of good information on
the Internet about it.

Best wishes,
Andrew

>
> But... no such luck:
>
> error: 'class cellml_apiIModel' has no member named 'localComponents'
>
> So how do I get at those functions like 'localComponents' that I used to
> be able to call when 'mod' was a cellml_api::Model* ?
>
> -Lucian
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