[−][src]Struct serde::de::IgnoredAny
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.
ⓘThis code runs with edition 2018
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<'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_u64<E>(self, x: u64) -> 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_i128<E>(self, v: i128) -> 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_u128<E>(self, v: u128) -> 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,
impl Clone for IgnoredAny
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fn clone(&self) -> IgnoredAny
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fn clone_from(&mut self, source: &Self)
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impl Copy for IgnoredAny
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impl Default for IgnoredAny
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fn default() -> IgnoredAny
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impl Debug for IgnoredAny
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Auto Trait Implementations
impl Send for IgnoredAny
impl Sync for IgnoredAny
impl Unpin for IgnoredAny
impl UnwindSafe for IgnoredAny
impl RefUnwindSafe for IgnoredAny
Blanket Implementations
impl<'de, T> Expected for T where
T: Visitor<'de>,
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T: Visitor<'de>,
impl<T> DeserializeOwned for T where
T: Deserialize<'de>,
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T: Deserialize<'de>,
impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> From<T> for T
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impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
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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.
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>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
ⓘImportant traits for &'_ mut Wfn borrow_mut(&mut self) -> &mut T
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ⓘImportant traits for &'_ mut W
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,