# Struct serde::de::IgnoredAny

source · [−]

    pub struct IgnoredAny;

Expand description

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

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### impl Clone for IgnoredAny

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#### fn clone(&self) -> IgnoredAny

Returns a copy of the value. Read more

1.0.0 · source

#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more

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### impl Debug for IgnoredAny

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

Formats the value using the given formatter. Read more

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### impl Default for IgnoredAny

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#### fn default() -> IgnoredAny

Returns the “default value” for a type. Read more

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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>,

Deserialize this value from the given Serde deserializer. Read more

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### impl<'de> Visitor<'de> for IgnoredAny

#### type Value = IgnoredAny

The value produced by this visitor.

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

Format a message stating what data this Visitor expects to receive. Read more

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#### fn visit_bool<E>(self, x: bool) -> Result<Self::Value, E>

The input contains a boolean. Read more

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#### fn visit_i64<E>(self, x: i64) -> Result<Self::Value, E>

The input contains an `i64`. Read more

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#### fn visit_i128<E>(self, x: i128) -> Result<Self::Value, E>

The input contains a `i128`. Read more

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#### fn visit_u64<E>(self, x: u64) -> Result<Self::Value, E>

The input contains a `u64`. Read more

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#### fn visit_u128<E>(self, x: u128) -> Result<Self::Value, E>

The input contains a `u128`. Read more

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#### fn visit_f64<E>(self, x: f64) -> Result<Self::Value, E>

The input contains an `f64`. Read more

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#### fn visit_str<E>(self, s: &str) -> Result<Self::Value, E> where
E: Error,

The input contains a string. The lifetime of the string is ephemeral and it may be destroyed after this method returns. Read more

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#### fn visit_none<E>(self) -> Result<Self::Value, E>

The input contains an optional that is absent. Read more

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#### fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error> where
D: Deserializer<'de>,

The input contains an optional that is present. Read more

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#### fn visit_newtype_struct<D>(
self,
deserializer: D
) -> Result<Self::Value, D::Error> where
D: Deserializer<'de>,

The input contains a newtype struct. Read more

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#### fn visit_unit<E>(self) -> Result<Self::Value, E>

The input contains a unit `()`. Read more

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#### fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error> where
A: SeqAccess<'de>,

The input contains a sequence of elements. Read more

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#### fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error> where
A: MapAccess<'de>,

The input contains a key-value map. Read more

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#### fn visit_bytes<E>(self, bytes: &[u8]) -> Result<Self::Value, E> where
E: Error,

The input contains a byte array. The lifetime of the byte array is ephemeral and it may be destroyed after this method returns. Read more

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#### fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error> where
A: EnumAccess<'de>,

The input contains an enum. Read more

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#### fn visit_i8<E>(self, v: i8) -> Result<Self::Value, E> where
E: Error,

The input contains an `i8`. Read more

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#### fn visit_i16<E>(self, v: i16) -> Result<Self::Value, E> where
E: Error,

The input contains an `i16`. Read more

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#### fn visit_i32<E>(self, v: i32) -> Result<Self::Value, E> where
E: Error,

The input contains an `i32`. Read more

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#### fn visit_u8<E>(self, v: u8) -> Result<Self::Value, E> where
E: Error,

The input contains a `u8`. Read more

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#### fn visit_u16<E>(self, v: u16) -> Result<Self::Value, E> where
E: Error,

The input contains a `u16`. Read more

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#### fn visit_u32<E>(self, v: u32) -> Result<Self::Value, E> where
E: Error,

The input contains a `u32`. Read more

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#### fn visit_f32<E>(self, v: f32) -> Result<Self::Value, E> where
E: Error,

The input contains an `f32`. Read more

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#### fn visit_char<E>(self, v: char) -> Result<Self::Value, E> where
E: Error,

The input contains a `char`. Read more

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#### fn visit_borrowed_str<E>(self, v: &'de str) -> Result<Self::Value, E> where
E: Error,

The input contains a string that lives at least as long as the `Deserializer`. Read more

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#### fn visit_string<E>(self, v: String) -> Result<Self::Value, E> where
E: Error,

The input contains a string and ownership of the string is being given to the `Visitor`. Read more

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#### fn visit_borrowed_bytes<E>(self, v: &'de [u8]) -> Result<Self::Value, E> where
E: Error,

The input contains a byte array that lives at least as long as the `Deserializer`. Read more

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#### fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E> where
E: Error,

The input contains a byte array and ownership of the byte array is being given to the `Visitor`. Read more

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### impl Copy for IgnoredAny

## 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

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### impl<T> Any for T where
T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

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### impl<T> Borrow<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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### impl<T> BorrowMut<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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### impl<'de, T> Expected for T where
T: Visitor<'de>,

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

Format an explanation of what data was being expected. Same signature as the `Display` and `Debug` traits. Read more

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for T where
T: Clone,

#### type Owned = T

The resulting type after obtaining ownership.

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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more

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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

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### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

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### impl<T> DeserializeOwned for T where
T: for<'de> Deserialize<'de>,