Is there a way to get the specific Tag implementation from the generic one?

[Sander Jansen]

Here's what I use in my music player:

https://github.com/gogglesmm/gogglesmm/blob/develop/src/GMTag.cpp#L609

Basically, dynamic_casts to get the specific tag container and then query
specific things from it.

On Sat, Sep 27, 2014 at 7:23 PM, Bill Fraser <bill.fraser at gmail.com> wrote:

> Hello,
>
> I'm using TagLib in a program which, among other things, needs to get the
> "albumartist" field from a bunch of music in different formats.
>
> I see that the TagLib::Tag generic interface doesn't contain albumartist
> (presumably because not all tag types have this property), but a number of
> the specific Tag implementations do have it (ID3v2 and XiphComment, at
> least).
>
> To get at this property, the first thing I tried was to use the generic
> Tag's properties() method and look for an "albumartist" property, but this
> doesn't work (though it does work on ID3v2 and XiphComment).
>
> The next thing I tried was to take the Tag pointer returned by File and
> dynamic_cast it to ID3v2::Tag*, XiphComment::Tag*, etc., so I could use
> their properties() methods, but this doesn't work either.
>
> So it looks like the only way to get this is to figure out the file type
> myself (based on file extension or whatever) and instantiate the specific
> Tag implementation myself. This seems kind of round-about to me, since
> obviously the generic Tag implementation has to do this already to provide
> me the few fields that it's capable of.
>
> So my questions are:
> 1. Why doesn't generic Tag::properties() work with "albumartist"?
> 2. How can I get at the specific Tag implementation being used?
>
> Everything else I've done with TagLib has been freaking awesome. I love
> how I don't have to do file type detection -- everything else just works --
> so I'll be rather disappointed if I have to start doing that.
>
> Thanks!
>
> --
> Bill Fraser { http://www.codewise.org/wrf }
>
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>
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