[−][src]Trait serde::Deserializer

pub trait Deserializer<'de>: Sized {
    type Error: Error;
    pub fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_bool<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_char<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_string<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_bytes<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_byte_buf<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_option<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_unit<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_unit_struct<V>(
        self, 
        name: &'static str, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_newtype_struct<V>(
        self, 
        name: &'static str, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_tuple<V>(
        self, 
        len: usize, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_tuple_struct<V>(
        self, 
        name: &'static str, 
        len: usize, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

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

    pub fn deserialize_enum<V>(
        self, 
        name: &'static str, 
        variants: &'static [&'static str], 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_identifier<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_ignored_any<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>;

    pub fn deserialize_i128<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    { ... }

    pub fn deserialize_u128<V>(
        self, 
        visitor: V
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    { ... }

    pub fn is_human_readable(&self) -> bool { ... }
}
[−]

A data format that can deserialize any data structure supported by Serde.

The role of this trait is to define the deserialization half of the Serde data model, which is a way to categorize every Rust data type into one of 29 possible types. Each method of the Deserializer trait corresponds to one of the types of the data model.

Implementations of Deserialize map themselves into this data model by passing to the Deserializer a Visitor implementation that can receive these various types.

The types that make up the Serde data model are:

The Deserializer trait supports two entry point styles which enables different kinds of deserialization.

  1. The deserialize method. Self-describing data formats like JSON are able to look at the serialized data and tell what it represents. For example the JSON deserializer may see an opening curly brace ({) and know that it is seeing a map. If the data format supports Deserializer::deserialize_any, it will drive the Visitor using whatever type it sees in the input. JSON uses this approach when deserializing serde_json::Value which is an enum that can represent any JSON document. Without knowing what is in a JSON document, we can deserialize it to serde_json::Value by going through Deserializer::deserialize_any.

  2. The various deserialize_* methods. Non-self-describing formats like Bincode need to be told what is in the input in order to deserialize it. The deserialize_* methods are hints to the deserializer for how to interpret the next piece of input. Non-self-describing formats are not able to deserialize something like serde_json::Value which relies on Deserializer::deserialize_any.

When implementing Deserialize, you should avoid relying on Deserializer::deserialize_any unless you need to be told by the Deserializer what type is in the input. Know that relying on Deserializer::deserialize_any means your data type will be able to deserialize from self-describing formats only, ruling out Bincode and many others.

Lifetime

The 'de lifetime of this trait is the lifetime of data that may be borrowed from the input when deserializing. See the page Understanding deserializer lifetimes for a more detailed explanation of these lifetimes.

Example implementation

The example data format presented on the website contains example code for a basic JSON Deserializer.

Associated Types

type Error: Error[src][−]

The error type that can be returned if some error occurs during deserialization.

Required methods

pub fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Require the Deserializer to figure out how to drive the visitor based on what data type is in the input.

When implementing Deserialize, you should avoid relying on Deserializer::deserialize_any unless you need to be told by the Deserializer what type is in the input. Know that relying on Deserializer::deserialize_any means your data type will be able to deserialize from self-describing formats only, ruling out Bincode and many others.

pub fn deserialize_bool<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a bool value.

pub fn deserialize_i8<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an i8 value.

pub fn deserialize_i16<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an i16 value.

pub fn deserialize_i32<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an i32 value.

pub fn deserialize_i64<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an i64 value.

pub fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a u8 value.

pub fn deserialize_u16<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a u16 value.

pub fn deserialize_u32<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a u32 value.

pub fn deserialize_u64<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a u64 value.

pub fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a f32 value.

pub fn deserialize_f64<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a f64 value.

pub fn deserialize_char<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a char value.

pub fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a string value and does not benefit from taking ownership of buffered data owned by the Deserializer.

If the Visitor would benefit from taking ownership of String data, indiciate this to the Deserializer by using deserialize_string instead.

pub fn deserialize_string<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a string value and would benefit from taking ownership of buffered data owned by the Deserializer.

If the Visitor would not benefit from taking ownership of String data, indicate that to the Deserializer by using deserialize_str instead.

pub fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a byte array and does not benefit from taking ownership of buffered data owned by the Deserializer.

If the Visitor would benefit from taking ownership of Vec<u8> data, indicate this to the Deserializer by using deserialize_byte_buf instead.

pub fn deserialize_byte_buf<V>(
    self,
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a byte array and would benefit from taking ownership of buffered data owned by the Deserializer.

If the Visitor would not benefit from taking ownership of Vec<u8> data, indicate that to the Deserializer by using deserialize_bytes instead.

pub fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an optional value.

This allows deserializers that encode an optional value as a nullable value to convert the null value into None and a regular value into Some(value).

pub fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a unit value.

pub fn deserialize_unit_struct<V>(
    self,
    name: &'static str,
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a unit struct with a particular name.

pub fn deserialize_newtype_struct<V>(
    self,
    name: &'static str,
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a newtype struct with a particular name.

pub fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a sequence of values.

pub fn deserialize_tuple<V>(
    self,
    len: usize,
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a sequence of values and knows how many values there are without looking at the serialized data.

pub fn deserialize_tuple_struct<V>(
    self,
    name: &'static str,
    len: usize,
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a tuple struct with a particular name and number of fields.

pub fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a map of key-value pairs.

pub fn deserialize_struct<V>(
    self,
    name: &'static str,
    fields: &'static [&'static str],
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting a struct with a particular name and fields.

pub fn deserialize_enum<V>(
    self,
    name: &'static str,
    variants: &'static [&'static str],
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an enum value with a particular name and possible variants.

pub fn deserialize_identifier<V>(
    self,
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting the name of a struct field or the discriminant of an enum variant.

pub fn deserialize_ignored_any<V>(
    self,
    visitor: V
) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type needs to deserialize a value whose type doesn't matter because it is ignored.

Deserializers for non-self-describing formats may not support this mode.

Provided methods

pub fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an i128 value.

This method is available only on Rust compiler versions >=1.26. The default behavior unconditionally returns an error.

pub fn deserialize_u128<V>(self, visitor: V) -> Result<V::Value, Self::Error> where
    V: Visitor<'de>, [src][−]

Hint that the Deserialize type is expecting an u128 value.

This method is available only on Rust compiler versions >=1.26. The default behavior unconditionally returns an error.

pub fn is_human_readable(&self) -> bool[src][−]

Determine whether Deserialize implementations should expect to deserialize their human-readable form.

Some types have a human-readable form that may be somewhat expensive to construct, as well as a binary form that is compact and efficient. Generally text-based formats like JSON and YAML will prefer to use the human-readable one and binary formats like Bincode will prefer the compact one.

ⓘThis code runs with edition 2018
use serde::de::{self, Deserialize, Deserializer};

impl<'de> Deserialize<'de> for Timestamp {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        if deserializer.is_human_readable() {
            // Deserialize from a human-readable string like "2015-05-15T17:01:00Z".
            let s = String::deserialize(deserializer)?;
            Timestamp::from_str(&s).map_err(de::Error::custom)
        } else {
            // Deserialize from a compact binary representation, seconds since
            // the Unix epoch.
            let n = u64::deserialize(deserializer)?;
            Ok(Timestamp::EPOCH + Duration::seconds(n))
        }
    }
}

The default implementation of this method returns true. Data formats may override this to false to request a compact form for types that support one. Note that modifying this method to change a format from human-readable to compact or vice versa should be regarded as a breaking change, as a value serialized in human-readable mode is not required to deserialize from the same data in compact mode.

Implementors

impl<'de, 'a, E> Deserializer<'de> for CowStrDeserializer<'a, E> where
    E: Error, [src][+]

type Error = E

impl<'de, 'a, E> Deserializer<'de> for StrDeserializer<'a, E> where
    E: Error, [src][+]

type Error = E

impl<'de, A> Deserializer<'de> for MapAccessDeserializer<A> where
    A: MapAccess<'de>, [src][+]

type Error = A::Error

impl<'de, A> Deserializer<'de> for SeqAccessDeserializer<A> where
    A: SeqAccess<'de>, [src][+]

type Error = A::Error

impl<'de, E> Deserializer<'de> for BoolDeserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for BorrowedBytesDeserializer<'de, E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for BorrowedStrDeserializer<'de, E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for CharDeserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for F32Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for F64Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for I8Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for I16Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for I32Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for I64Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for I128Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for IsizeDeserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for StringDeserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for U8Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for U16Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for U32Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for U64Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for U128Deserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for UnitDeserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, E> Deserializer<'de> for UsizeDeserializer<E> where
    E: Error, [src][+]

type Error = E

impl<'de, I, E> Deserializer<'de> for MapDeserializer<'de, I, E> where
    I: Iterator,
    I::Item: Pair,
    <I::Item as Pair>::First: IntoDeserializer<'de, E>,
    <I::Item as Pair>::Second: IntoDeserializer<'de, E>,
    E: Error, [src][+]

type Error = E

impl<'de, I, T, E> Deserializer<'de> for SeqDeserializer<I, E> where
    I: Iterator<Item = T>,
    T: IntoDeserializer<'de, E>,
    E: Error, [src][+]

type Error = E