Struct serde::de::IgnoredAny [−][src]
An efficient way of discarding data from a deserializer.
Think of this like serde_json::Value
in that it can be deserialized from
any type, except that it does not store any information about the data that
gets deserialized.
ⓘ
use std::fmt; use std::marker::PhantomData; use serde::de::{ self, Deserialize, DeserializeSeed, Deserializer, IgnoredAny, SeqAccess, Visitor, }; /// A seed that can be used to deserialize only the `n`th element of a sequence /// while efficiently discarding elements of any type before or after index `n`. /// /// For example to deserialize only the element at index 3: /// /// ``` /// NthElement::new(3).deserialize(deserializer) /// ``` pub struct NthElement<T> { n: usize, marker: PhantomData<T>, } impl<T> NthElement<T> { pub fn new(n: usize) -> Self { NthElement { n: n, marker: PhantomData, } } } impl<'de, T> Visitor<'de> for NthElement<T> where T: Deserialize<'de>, { type Value = T; fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result { write!( formatter, "a sequence in which we care about element {}", self.n ) } fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error> where A: SeqAccess<'de>, { // Skip over the first `n` elements. for i in 0..self.n { // It is an error if the sequence ends before we get to element `n`. if seq.next_element::<IgnoredAny>()?.is_none() { return Err(de::Error::invalid_length(i, &self)); } } // Deserialize the one we care about. let nth = match seq.next_element()? { Some(nth) => nth, None => { return Err(de::Error::invalid_length(self.n, &self)); } }; // Skip over any remaining elements in the sequence after `n`. while let Some(IgnoredAny) = seq.next_element()? { // ignore } Ok(nth) } } impl<'de, T> DeserializeSeed<'de> for NthElement<T> where T: Deserialize<'de>, { type Value = T; fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error> where D: Deserializer<'de>, { deserializer.deserialize_seq(self) } } // Deserialize only the sequence element at index 3 from this deserializer. // The element at index 3 is required to be a string. Elements before and // after index 3 are allowed to be of any type. let s: String = NthElement::new(3).deserialize(deserializer)?;
Trait Implementations
impl Clone for IgnoredAny
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fn clone(&self) -> IgnoredAny
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pub fn clone_from(&mut self, source: &Self)
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impl Copy for IgnoredAny
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impl Debug for IgnoredAny
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impl Default for IgnoredAny
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fn default() -> IgnoredAny
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impl<'de> Deserialize<'de> for IgnoredAny
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fn deserialize<D>(deserializer: D) -> Result<IgnoredAny, D::Error> where
D: Deserializer<'de>,
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D: Deserializer<'de>,
impl<'de> Visitor<'de> for IgnoredAny
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type Value = IgnoredAny
The value produced by this visitor.
fn expecting(&self, formatter: &mut Formatter<'_>) -> Result
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fn visit_bool<E>(self, x: bool) -> Result<Self::Value, E>
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fn visit_i64<E>(self, x: i64) -> Result<Self::Value, E>
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fn visit_i128<E>(self, x: i128) -> Result<Self::Value, E>
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fn visit_u64<E>(self, x: u64) -> Result<Self::Value, E>
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fn visit_u128<E>(self, x: u128) -> Result<Self::Value, E>
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fn visit_f64<E>(self, x: f64) -> Result<Self::Value, E>
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fn visit_str<E>(self, s: &str) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_none<E>(self) -> Result<Self::Value, E>
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fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error> where
D: Deserializer<'de>,
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D: Deserializer<'de>,
fn visit_newtype_struct<D>(
self,
deserializer: D
) -> Result<Self::Value, D::Error> where
D: Deserializer<'de>,
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self,
deserializer: D
) -> Result<Self::Value, D::Error> where
D: Deserializer<'de>,
fn visit_unit<E>(self) -> Result<Self::Value, E>
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fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error> where
A: SeqAccess<'de>,
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A: SeqAccess<'de>,
fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error> where
A: MapAccess<'de>,
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A: MapAccess<'de>,
fn visit_bytes<E>(self, bytes: &[u8]) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error> where
A: EnumAccess<'de>,
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A: EnumAccess<'de>,
fn visit_i8<E>(self, v: i8) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_i16<E>(self, v: i16) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_i32<E>(self, v: i32) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_u8<E>(self, v: u8) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_u16<E>(self, v: u16) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_u32<E>(self, v: u32) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_f32<E>(self, v: f32) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_char<E>(self, v: char) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_borrowed_str<E>(self, v: &'de str) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_string<E>(self, v: String) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_borrowed_bytes<E>(self, v: &'de [u8]) -> Result<Self::Value, E> where
E: Error,
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E: Error,
fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E> where
E: Error,
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E: Error,
Auto Trait Implementations
impl RefUnwindSafe for IgnoredAny
impl Send for IgnoredAny
impl Sync for IgnoredAny
impl Unpin for IgnoredAny
impl UnwindSafe for IgnoredAny
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow(&self) -> &TⓘNotable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
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Notable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
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Notable traits for &'_ mut R
impl<'_, R> Read for &'_ mut R where
R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
W: Write + ?Sized, impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;
impl<T> DeserializeOwned for T where
T: for<'de> Deserialize<'de>,
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T: for<'de> Deserialize<'de>,
impl<'de, T> Expected for T where
T: Visitor<'de>,
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T: Visitor<'de>,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
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pub fn clone_into(&self, target: &mut T)
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,