How to get enum id to be written when it's on the outer struct?

[yanshay]

In the below struct, the enum id is based on the outer struct field data_type.
When I write I want the data_type to be filled based on the enum variant in the data field.
How can I do that? Couldn't find an automated way and couldn't find how to access the deku id of the enum to fill it on update.

Also, while here, is there a way to place 'magic' inside a struct and not only as prefix to the struct? (that's the last field on the struct which is always 10). I could make a struct out of that field but seems like it should be simpler.

#[derive(Debug, PartialEq, DekuRead, DekuWrite)]
#[deku(ctx ="data_type: u8", id = "data_type")]
enum ImprovWifiPacketData {
   #[deku(id=0x02)]
   RPC(u32)
}

#[derive(Debug, PartialEq, DekuRead, DekuWrite)]
#[deku(magic=b"IMPROV\x01")]
struct ImprovWifiPacket {
    data_type: u8,
    data_len: u8,
    #[deku(ctx = "*data_type")]
    data: ImprovWifiPacketData,
    checksum: u8,
    #[deku(update="10")]
    always_ten: u8,
}

[wcampbell0x2a]

The MR to add ctx to update is here: #415. I haven't work on it in awhile, I think you may have asked for something like this before in another issue!

The magic can just be an assert on a field in the struct.

[wcampbell0x2a]

Create a struct with its own magic and put it there (which is what I chose so not to have to remember to call update every time)

This is what I do, have a const value, then assert it for "magic".

[wcampbell0x2a]

What I did now was implement on the enum a get_id and I call it from the writer (and I do it for several enums which clutters the code). But this means the Id's are supplied twice, both to deku and in the get_id method.

We do have an deku_id function: https://docs.rs/deku/latest/deku/trait.DekuEnumExt.html, It wont be emitted for generics.

[yanshay]

Great, thanks. That's exactly what I was looking for.

[yanshay]

Create a struct with its own magic and put it there (which is what I chose so not to have to remember to call update every time)

This is what I do, have a const value, then assert it for "magic".

What do you mean by const? afaik rust doesn't support const struct fields. Maybe you refer to setting it to const in a new fn that initializes the struct? I may have several different new so I would need to set it in several places.

[wcampbell0x2a]

You're right, I push an MR that does "field magic": #503