Trait serde::de::VariantVisitor

pub trait VariantVisitor: Sized {
    type Error: Error;
    fn visit_unit(self) -> Result<(), Self::Error>;
    fn visit_newtype_seed<T>(self, seed: T) -> Result<T::Value, Self::Error>
    where
        T: DeserializeSeed;
    fn visit_tuple<V>(
        self, 
        len: usize, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor;
    fn visit_struct<V>(
        self, 
        fields: &'static [&'static str], 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor;

    fn visit_newtype<T>(self) -> Result<T, Self::Error>
    where
        T: Deserialize,
    { ... }
}

VariantVisitor is a visitor that is created by the Deserializer and passed to the Deserialize to deserialize the content of a particular enum variant.

Associated Types

type Error: Error

The error type that can be returned if some error occurs during deserialization. Must match the error type of our EnumVisitor.

Required Methods

fn visit_unit(self) -> Result<(), Self::Error>

Called when deserializing a variant with no values.

If the data contains a different type of variant, the following invalid_type error should be constructed:

fn visit_unit(self) -> Result<(), Self::Error> {
    // What the data actually contained; suppose it is a tuple variant.
    let unexp = Unexpected::TupleVariant;
    Err(de::Error::invalid_type(unexp, &"unit variant"))
}

fn visit_newtype_seed<T>(self, seed: T) -> Result<T::Value, Self::Error> where
    T: DeserializeSeed, 

Called when deserializing a variant with a single value.

Deserialize implementations should typically use VariantVisitor::visit_newtype instead.

If the data contains a different type of variant, the following invalid_type error should be constructed:

fn visit_newtype_seed<T>(self, _seed: T) -> Result<T::Value, Self::Error>
    where T: de::DeserializeSeed
{
    // What the data actually contained; suppose it is a unit variant.
    let unexp = Unexpected::UnitVariant;
    Err(de::Error::invalid_type(unexp, &"newtype variant"))
}

fn visit_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor, 

Called when deserializing a tuple-like variant.

The len is the number of fields expected in the tuple variant.

If the data contains a different type of variant, the following invalid_type error should be constructed:

fn visit_tuple<V>(self,
                  _len: usize,
                  _visitor: V) -> Result<V::Value, Self::Error>
    where V: Visitor
{
    // What the data actually contained; suppose it is a unit variant.
    let unexp = Unexpected::UnitVariant;
    Err(Error::invalid_type(unexp, &"tuple variant"))
}

fn visit_struct<V>(
    self,
    fields: &'static [&'static str],
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor, 

Called when deserializing a struct-like variant.

The fields are the names of the fields of the struct variant.

If the data contains a different type of variant, the following invalid_type error should be constructed:

fn visit_struct<V>(self,
                   _fields: &'static [&'static str],
                   _visitor: V) -> Result<V::Value, Self::Error>
    where V: Visitor
{
    // What the data actually contained; suppose it is a unit variant.
    let unexp = Unexpected::UnitVariant;
    Err(Error::invalid_type(unexp, &"struct variant"))
}

Provided Methods

fn visit_newtype<T>(self) -> Result<T, Self::Error> where
    T: Deserialize, 

Called when deserializing a variant with a single value.

This method exists as a convenience for Deserialize implementations. VariantVisitor implementations should not override the default behavior.

Implementors