Struct PyWeakrefReference

Source

pub struct PyWeakrefReference(/* private fields */);

Expand description

Represents a Python weakref.ReferenceType.

In Python this is created by calling weakref.ref.

Implementations§

Source §

impl PyWeakrefReference

Source

pub fn new_bound<'py>( object: &Bound<'py, PyAny>, ) -> PyResult<Bound<'py, PyWeakrefReference>>

Constructs a new Weak Reference (weakref.ref/weakref.ReferenceType) for the given object.

Returns a TypeError if object is not weak referenceable (Most native types and PyClasses without weakref flag).

§Examples

use pyo3::prelude::*;
use pyo3::types::PyWeakrefReference;

#[pyclass(weakref)]
struct Foo { /* fields omitted */ }

Python::with_gil(|py| {
    let foo = Bound::new(py, Foo {})?;
    let weakref = PyWeakrefReference::new_bound(&foo)?;
    assert!(
        // In normal situations where a direct `Bound<'py, Foo>` is required use `upgrade::<Foo>`
        weakref.upgrade()
            .map_or(false, |obj| obj.is(&foo))
    );

    let weakref2 = PyWeakrefReference::new_bound(&foo)?;
    assert!(weakref.is(&weakref2));

    drop(foo);

    assert!(weakref.upgrade().is_none());
    Ok(())
})

Source

pub fn new_bound_with<'py, C>( object: &Bound<'py, PyAny>, callback: C, ) -> PyResult<Bound<'py, PyWeakrefReference>>
where C: ToPyObject,

Constructs a new Weak Reference (weakref.ref/weakref.ReferenceType) for the given object with a callback.

Returns a TypeError if object is not weak referenceable (Most native types and PyClasses without weakref flag) or if the callback is not callable or None.

§Examples

use pyo3::prelude::*;
use pyo3::types::PyWeakrefReference;

#[pyclass(weakref)]
struct Foo { /* fields omitted */ }

#[pyfunction]
fn callback(wref: Bound<'_, PyWeakrefReference>) -> PyResult<()> {
        let py = wref.py();
        assert!(wref.upgrade_as::<Foo>()?.is_none());
        py.run_bound("counter = 1", None, None)
}

Python::with_gil(|py| {
    py.run_bound("counter = 0", None, None)?;
    assert_eq!(py.eval_bound("counter", None, None)?.extract::<u32>()?, 0);
    let foo = Bound::new(py, Foo{})?;

    // This is fine.
    let weakref = PyWeakrefReference::new_bound_with(&foo, py.None())?;
    assert!(weakref.upgrade_as::<Foo>()?.is_some());
    assert!(
        // In normal situations where a direct `Bound<'py, Foo>` is required use `upgrade::<Foo>`
        weakref.upgrade()
            .map_or(false, |obj| obj.is(&foo))
    );
    assert_eq!(py.eval_bound("counter", None, None)?.extract::<u32>()?, 0);

    let weakref2 = PyWeakrefReference::new_bound_with(&foo, wrap_pyfunction_bound!(callback, py)?)?;
    assert!(!weakref.is(&weakref2)); // Not the same weakref
    assert!(weakref.eq(&weakref2)?);  // But Equal, since they point to the same object

    drop(foo);

    assert!(weakref.upgrade_as::<Foo>()?.is_none());
    assert_eq!(py.eval_bound("counter", None, None)?.extract::<u32>()?, 1);
    Ok(())
})