Trait UnsizedVisitor

pub trait UnsizedVisitor<'de, C: ?Sized + Context, T>: Sized
where
    T: ?Sized + ToOwned,
{
    type Ok;

    // Required method
    fn expecting(&self, f: &mut Formatter<'_>) -> Result;

    // Provided methods
    fn visit_owned(self, cx: &C, value: T::Owned) -> Result<Self::Ok, C::Error> { ... }
    fn visit_borrowed(self, cx: &C, value: &'de T) -> Result<Self::Ok, C::Error> { ... }
    fn visit_ref(self, cx: &C, _: &T) -> Result<Self::Ok, C::Error> { ... }
}

A visitor for data where we might need to borrow without copying from the underlying Decoder.

A visitor is needed with Decoder::decode_bytes and Decoder::decode_string because the caller doesn’t know if the encoding format is capable of producing references to the underlying data directly or if it needs to be processed first.

If all you want is to decode a value by reference, use the Decoder::decode_unsized method.

By requiring a visitor we ensure that the caller has to handle both scenarios, even if one involves erroring. A type like Cow is an example of a type which can comfortably handle both.

Required Associated Types

type Ok

The value produced.

Required Methods

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

Format an error indicating what was expected by this visitor.

Override to be more specific about the type that failed.

Provided Methods

fn visit_owned(self, cx: &C, value: T::Owned) -> Result<Self::Ok, C::Error>

Visit an owned value.

fn visit_borrowed(self, cx: &C, value: &'de T) -> Result<Self::Ok, C::Error>

Visit a string that is borrowed directly from the source data.

fn visit_ref(self, cx: &C, _: &T) -> Result<Self::Ok, C::Error>

Visit a value reference that is provided from the decoder in any manner possible. Which might require additional decoding work.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors