How do I return self in a function within a class?

[yuhime]

#[pyclass]
struct Test {
    lines: Vec<String>,
}

#[pymethods]
impl Test {
    #[new]
    fn __new__() -> Self {
        Test { lines: Vec::new() }
    }

    fn add_line(&mut self, value: String, py: Python) -> PyResult<&mut Self> {
        self.lines.push(value);

        Ok(self)
    }
}

I tried everything but couldn't get it done
(I am new to rust)

the result should be:

a = Test()
a.add_line("some").add_line() ...

Is just an example to understand how it should work

[davidhewitt]

I think you want this code:

#[pyclass]
struct Test {
    lines: Vec<String>,
}

#[pymethods]
impl Test {
    #[new]
    fn __new__() -> Self {
        Test { lines: Vec::new() }
    }

    fn add_line<'a>(slf: PyRefMut<'a, Self>, value: String, py: Python) -> PyResult<PyRefMut<'a, Self>> {
        slf.lines.push(value);

        Ok(slf)
    }
}

The PyRefMut type is a wrapper around the Python-owned data, and so returning it back out from the function works in the way you want for chaining.

[yuhime]

It works thank you!