dbus[22875]: Array or variant type requires that type begin_struct be written, but double was written.

[mdgaziur]

Having problem with sending a Vector of a struct. Getting the following error. Any help?

Error:

dbus[22875]: Array or variant type requires that type begin_struct be written, but double was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.
dbus[22875]: Array or variant type requires that type begin_struct be written, but string was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.
dbus[22875]: Array or variant type requires that type begin_struct be written, but string was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.
dbus[22875]: Array or variant type requires that type begin_struct be written, but string was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.
dbus[22875]: Array or variant type requires that type begin_struct be written, but double was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.
dbus[22875]: Array or variant type requires that type begin_struct be written, but string was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.
dbus[22875]: Array or variant type requires that type begin_struct be written, but string was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.
dbus[22875]: Array or variant type requires that type begin_struct be written, but string was written.
The overall signature expected here was 'a(dsss)' and we are on byte 1 of that signature.

Request:
dbus-send --print-reply --dest=org.findex.daemon "/get_result" "org.findex.daemon.query.get_result" string:'test'

Return Payload:

method return time=1641014639.834411 sender=:1.550 -> destination=:1.551 serial=8 reply_serial=2
   array [
      struct {
         double 0.1
         string "FakeApp"
         string "fake"
         string "other"
      }
      struct {
         double 0.1
         string "FakeApp"
         string "fake"
         string "other"
      }
   ]

Struct Implementation:

#[derive(Debug, Clone)]
pub struct AppInfo {
    pub total_score: f64,
    pub name: String,
    pub exec: String,
    pub icon: String,
}

impl Arg for AppInfo {
    const ARG_TYPE: ArgType = ArgType::Struct;

    fn signature() -> Signature<'static> {
        Signature::new("(dsss)").unwrap()
    }
}

impl Append for AppInfo {
    fn append_by_ref(&self, ia: &mut IterAppend){
        self.total_score.append(ia);
        self.name.as_str().append(ia);
        self.exec.as_str().append(ia);
        self.icon.as_str().append(ia);
    }
}

Method Implementation:

builder.method("get_result", ("query",), ("config",), move |_, _, (query,): (String,)| {
    let mut result = Vec::new();

    result.push(AppInfo {
        total_score: 0.1,
        name: String::from("FakeApp"),
        icon: String::from("other"),
        exec: String::from("fake")
    });

    result.push(AppInfo {
        total_score: 0.1,
        name: String::from("FakeApp"),
        icon: String::from("other"),
        exec: String::from("fake")
    });

    println!("{}", Vec::<AppInfo>::signature());

    Ok((result,))
});

[mulkieran]

@mdgaziur Before I get started, I'ld like to mention that I am not @diwic, and so much more likely to be wrong. However, as far as I can tell the problem that you are encountering is due to the fact that you have implemented Append for your AppInfo type incorrectly. Your Append implementation just destructures the struct into its individual parts. In the D-Bus spec, a "struct" is just a tuple. You need to hand it in the proper form to the append function. Something similar to this is likely to work better.

impl Append for AppInfo {
    fn append_by_ref(&self, ia: &mut IterAppend){
        (self.total_score, self.name, self.exec, self.icon).append(ia);
    }
}

I feel fairly confident that my suggestion won't compile, but it should do the correct thing once that is fixed.

[mdgaziur]

I'll check it soon :D

[mdgaziur]

Thanks for pointing out my mistake :D. It now works