Struct Saved 

pub struct Saved<'a, T: TypedExternal + ?Sized> {
    sexp: SEXP,
    _marker: PhantomData<&'a T>,
}

What a save of a T kept, handed to the type’s rebuild hook (#[externalptr(rebuild = path)]) when a pointer restored from a saved session is first used.

The type’s generated Sidecar getters read the saved values through it, as through a live handle: Self::keys(saved). Only Sidecar fields have a slot in the save; a struct field or a Computed field is gone with the Rust value, so a type whose rebuild needs one keeps it in a Sidecar.

The save names its slots after the fields’ R names (the #[r_data(name = "..")] value, else the Rust field name), so a field is read by name whatever fields the version that saved it had (#2187, #2215). A field the save lacks (added since) reads as None through the generated Self::try_keys(saved); the plain getter raises the classed error RESTORED_MISSING_SLOT_CLASS.

Fields

sexp: SEXP

_marker: PhantomData<&'a T>

Implementations

impl<T: TypedExternal + ?Sized> Saved<'_, T>

pub(crate) unsafe fn new(sexp: SEXP) -> Self

The handle over sexp, a pointer for a T restored without its value.

Safety

sexp must be a live EXTPTRSXP built by ExternalPtr for a T by some version of its crate, rooted for the handle’s lifetime.

pub fn as_sexp(&self) -> SEXP

The restored external pointer.

pub fn has(&self, field: &str) -> bool

Whether the save has a slot for the Sidecar field field, given by its R name: the #[r_data(name = "..")] value, else the Rust field name. The generated Self::try_<field>(saved) getters say the same with the field’s type, checked by the compiler.

The R name is the save format (#2215): a save names each slot after it. Renaming the Rust field keeps earlier saves readable; renaming the R name orphans the field’s slot in every earlier save, which then reads as a field the save lacks.

pub fn version(&self) -> Option<&'static str>

The version of the crate that saved the object, from the type ID the save recorded: the current version for a save this version made, an earlier (or later) one under any_version.

Trait Implementations

impl<T: TypedExternal + ?Sized> Debug for Saved<'_, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: TypedExternal + ?Sized> Owner for Saved<'_, T>

impl<T: TypedExternal + ?Sized> SidecarOwner<T> for Saved<'_, T>

fn __mx_read(&self) -> SidecarRead<'_, T>

The value, borrowed shared, with its R object; or, for a Saved handle, the restored pointer alone.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes