How to import Rust struct as a parameter of another Rust struct? (minimal example provided)

[shanmukhateja]

Hello,

I have 2 classes - class1.rs & class2.rs.

I am trying to use Class2 as a parameter for a qinvokable function inside class1.rs.

Please look at the code:

class1.rs

use std::pin::Pin;

use crate::{class1::qobject::Class1, class2::qobject::Class2};

#[cxx_qt::bridge]
pub mod qobject {

    unsafe extern "RustQt" {
        #[qobject]
        #[qml_element]
        type Class1 = super::Class1Rust;


        #[qinvokable]
        fn foo(self: Pin<&mut Class1>, class2: Pin<&Class2>);  // I get "Unsupported type" here.
    }
}

#[derive(Default)]
pub struct Class1Rust;

impl Class1Rust {
    fn append_item(mut self: Pin<&mut Class1>, class2: &Class2) {}
}

class2.rs

#[cxx_qt::bridge]
pub mod qobject {
    unsafe extern "RustQt" {
        #[qobject]
        #[qml_element]
        pub type Class2 = super::Class2Rust;
    }
}

#[derive(Default)]
pub struct Class2Rust;

What I have tried:

1. I tried declaring extern "Rust" { type Class2; } block but then it complains about "no throw destructors in Qt" or something.

2. I also tried declaring the type outside of qobject module (inside class1.rs) but that gives me a Pin related error.

[ahayzen-kdab]

The bridge in class1.rs still needs to be told about Class2. Then note that there are two types Class2 and Class2Rust, the first being an extern C++ type for the C++ side and the second being an extern Rust type. Whenever you are using ::qobject::T this is referring to the C++ type. So instead something like this should work, as also shown in the CXX docs https://cxx.rs/extern-c++.html#reusing-existing-binding-types

use std::pin::Pin;

use crate::{class1::qobject::Class1, class2::qobject::Class2};

#[cxx_qt::bridge]
pub mod qobject {
    unsafe extern "C++" {
        // define Class2 as a C++ type the same as the one from the other bridge
        // note that you may need to include the header of the file here too with include!("myheader.h");
        type Class2 = crate::class2::qobject::Class2;
    }

    unsafe extern "RustQt" {
        #[qobject]
        #[qml_element]
        type Class1 = super::Class1Rust;


        #[qinvokable]
        fn foo(self: Pin<&mut Class1>, class2: Pin<&Class2>);
    }
}

#[derive(Default)]
pub struct Class1Rust;

impl Class1Rust {
    fn append_item(mut self: Pin<&mut Class1>, class2: &Class2) {}
}