pub trait MapAccess<'de> {
type Error: Error;
// Required methods
fn next_key_seed<K>(
&mut self,
seed: K,
) -> Result<Option<<K as DeserializeSeed<'de>>::Value>, Self::Error>
where K: DeserializeSeed<'de>;
fn next_value_seed<V>(
&mut self,
seed: V,
) -> Result<<V as DeserializeSeed<'de>>::Value, Self::Error>
where V: DeserializeSeed<'de>;
// Provided methods
fn next_entry_seed<K, V>(
&mut self,
kseed: K,
vseed: V,
) -> Result<Option<(<K as DeserializeSeed<'de>>::Value, <V as DeserializeSeed<'de>>::Value)>, Self::Error>
where K: DeserializeSeed<'de>,
V: DeserializeSeed<'de> { ... }
fn next_key<K>(&mut self) -> Result<Option<K>, Self::Error>
where K: Deserialize<'de> { ... }
fn next_value<V>(&mut self) -> Result<V, Self::Error>
where V: Deserialize<'de> { ... }
fn next_entry<K, V>(&mut self) -> Result<Option<(K, V)>, Self::Error>
where K: Deserialize<'de>,
V: Deserialize<'de> { ... }
fn size_hint(&self) -> Option<usize> { ... }
}
Expand description
Provides a Visitor
access to each entry of a map in the input.
This is a trait that a Deserializer
passes to a Visitor
implementation.
§Lifetime
The 'de
lifetime of this trait is the lifetime of data that may be
borrowed by deserialized map entries. See the page Understanding
deserializer lifetimes for a more detailed explanation of these lifetimes.
§Example implementation
The example data format presented on the website demonstrates an
implementation of MapAccess
for a basic JSON data format.
Required Associated Types§
Required Methods§
sourcefn next_key_seed<K>(
&mut self,
seed: K,
) -> Result<Option<<K as DeserializeSeed<'de>>::Value>, Self::Error>where
K: DeserializeSeed<'de>,
fn next_key_seed<K>(
&mut self,
seed: K,
) -> Result<Option<<K as DeserializeSeed<'de>>::Value>, Self::Error>where
K: DeserializeSeed<'de>,
This returns Ok(Some(key))
for the next key in the map, or Ok(None)
if there are no more remaining entries.
Deserialize
implementations should typically use
MapAccess::next_key
or MapAccess::next_entry
instead.
sourcefn next_value_seed<V>(
&mut self,
seed: V,
) -> Result<<V as DeserializeSeed<'de>>::Value, Self::Error>where
V: DeserializeSeed<'de>,
fn next_value_seed<V>(
&mut self,
seed: V,
) -> Result<<V as DeserializeSeed<'de>>::Value, Self::Error>where
V: DeserializeSeed<'de>,
This returns a Ok(value)
for the next value in the map.
Deserialize
implementations should typically use
MapAccess::next_value
instead.
§Panics
Calling next_value_seed
before next_key_seed
is incorrect and is
allowed to panic or return bogus results.
Provided Methods§
sourcefn next_entry_seed<K, V>(
&mut self,
kseed: K,
vseed: V,
) -> Result<Option<(<K as DeserializeSeed<'de>>::Value, <V as DeserializeSeed<'de>>::Value)>, Self::Error>where
K: DeserializeSeed<'de>,
V: DeserializeSeed<'de>,
fn next_entry_seed<K, V>(
&mut self,
kseed: K,
vseed: V,
) -> Result<Option<(<K as DeserializeSeed<'de>>::Value, <V as DeserializeSeed<'de>>::Value)>, Self::Error>where
K: DeserializeSeed<'de>,
V: DeserializeSeed<'de>,
This returns Ok(Some((key, value)))
for the next (key-value) pair in
the map, or Ok(None)
if there are no more remaining items.
MapAccess
implementations should override the default behavior if a
more efficient implementation is possible.
Deserialize
implementations should typically use
MapAccess::next_entry
instead.
sourcefn next_key<K>(&mut self) -> Result<Option<K>, Self::Error>where
K: Deserialize<'de>,
fn next_key<K>(&mut self) -> Result<Option<K>, Self::Error>where
K: Deserialize<'de>,
This returns Ok(Some(key))
for the next key in the map, or Ok(None)
if there are no more remaining entries.
This method exists as a convenience for Deserialize
implementations.
MapAccess
implementations should not override the default behavior.
sourcefn next_value<V>(&mut self) -> Result<V, Self::Error>where
V: Deserialize<'de>,
fn next_value<V>(&mut self) -> Result<V, Self::Error>where
V: Deserialize<'de>,
This returns a Ok(value)
for the next value in the map.
This method exists as a convenience for Deserialize
implementations.
MapAccess
implementations should not override the default behavior.
§Panics
Calling next_value
before next_key
is incorrect and is allowed to
panic or return bogus results.
sourcefn next_entry<K, V>(&mut self) -> Result<Option<(K, V)>, Self::Error>where
K: Deserialize<'de>,
V: Deserialize<'de>,
fn next_entry<K, V>(&mut self) -> Result<Option<(K, V)>, Self::Error>where
K: Deserialize<'de>,
V: Deserialize<'de>,
This returns Ok(Some((key, value)))
for the next (key-value) pair in
the map, or Ok(None)
if there are no more remaining items.
This method exists as a convenience for Deserialize
implementations.
MapAccess
implementations should not override the default behavior.