How to setup popularimeter for id3v2?

[subframe7536]

Thanks for your great work!

I used to ask for wasm version in #400 and now I am building one myself but dont know how to setup POPM frame for id3v2

My code is here and I want to achieve something like

    /// The rate of the song
    #[wasm_bindgen(getter = rate)]
    pub fn get_rate(&self) -> Option<u8> {
        // how?
    }

    #[wasm_bindgen(setter = rate)]
    pub fn set_rate(&mut self, rate: u8) {
        if &self.tag.tag_type() == &TagType::Id3v2 {
            // how?
        } else {
            // how?
        }
    }

Any suggestion is highly appreciated!

[Serial-ATA]

So ItemKey::Popularimeter is very misleading and I actually have it removed for 0.20.0. It only existed to preserve the POPM frame between Id3v2Tag -> Tag conversions, as all versions before 0.20.0 would have a lossy conversion (#302).

I have been thinking of a way to add a generic Popularimeter struct, as it is something that exists in ID3v2, Vorbis Comments, Ilst, and WMA (when that eventually gets supported). For now though, you'll have to create an Id3v2Tag to use POPM frames:

let mut tag = Id3v2Tag::new();

tag.insert(Frame::new(
   "POPM",
   FrameType::Popularimeter(Popularimeter {
      email: String::new(),
      rating: 255,
      counter: 0,
    }),
   FrameFlags::default(),
).unwrap());

Note that Frame creation will change significantly in 0.20.0.

[Serial-ATA]

This should work:

let tag = Id3v2Tag::new();

tag.insert(Frame::Popularimeter(
  PopularimeterFrame::new(
    String::new(),
    255
    0
  )
));

[subframe7536]

I'm trying to convert generic Tag to Id3v2Tag but failed...

#[wasm_bindgen(setter = rate)]
pub fn set_rate(&mut self, rate: u8) {
    match &self.tag.tag_type() {
        &TagType::Id3v2 => {
            let mut id3v2: &Id3v2Tag = self.tag.into();
            //                                  ^Error
            id3v2.insert(Frame::Popularimeter(PopularimeterFrame::new(
                String::new(),
                rate,
                0,
            )));
        }
        &TagType::VorbisComments => {
            // todo))
        }
        &TagType::Mp4Ilst => {
            // todo))
        }
        &TagType::RiffInfo => {
            // todo))
        }
        _ => {}
    }
}

The error info is:

the trait bound `&Id3v2Tag: From<Tag>` is not satisfied
the following other types implement trait `From<T>`:
  <Id3v2Tag as From<Tag>>
  <Id3v2Tag as From<v2::tag::SplitTagRemainder>>
required for `Tag` to implement `Into<&Id3v2Tag>`

[Serial-ATA]

The issue is you're trying to convert to a **&**Id3v2Tag.

Instead of:

let mut id3v2: &Id3v2Tag = self.tag.into();

You'll need:

let mut id3v2: Id3v2Tag = self.tag.into();

[subframe7536]

Hmmm... another error prompt:

cannot move out of self.tag which is behind a mutable reference
move occurs because self.tag has type Tag, which does not implement the Copy

I just want to avoid redundant copy

[Serial-ATA]

With the way you're using Tag, you'll have to do self.tag.clone(). Into::<Id3v2Tag>::into() consumes the self.tag and converts it into an Id3v2Tag.

It'd probably be best in your case to wait until 0.21.0 when I make ItemKey::Popularimeter available so uou don't have to worry about converting tags.