Struct serde_with::OneOrMany
source · [−]Expand description
Deserialize one or many elements
Sometimes it is desirable to have a shortcut in writing 1-element lists in a config file.
Usually, this is done by either writing a list or the list element itself.
This distinction is not semantically important on the Rust side, thus both forms should serialize into the same Vec
.
The OneOrMany
adapter achieves exactly this use case.
The serialization behavior can be tweaked to either always serialize as a list using PreferMany
or to serialize as the inner element if possible using PreferOne
.
By default, PreferOne
is assumed, which can also be omitted like OneOrMany<_>
.
Examples
#[serde_as]
#[derive(Deserialize, serde::Serialize)]
struct Data {
#[serde_as(deserialize_as = "OneOrMany<_, PreferOne>")]
countries: Vec<String>,
#[serde_as(deserialize_as = "OneOrMany<_, PreferMany>")]
cities: Vec<String>,
}
// The adapter allows deserializing a `Vec` from either
// a single element
let j = json!({
"countries": "Spain",
"cities": "Berlin",
});
assert!(serde_json::from_value::<Data>(j).is_ok());
// or from a list.
let j = json!({
"countries": ["Germany", "France"],
"cities": ["Amsterdam"],
});
assert!(serde_json::from_value::<Data>(j).is_ok());
// For serialization you can choose how a single element should be encoded.
// Either directly, with `PreferOne` (default), or as a list with `PreferMany`.
let data = Data {
countries: vec!["Spain".to_string()],
cities: vec!["Berlin".to_string()],
};
let j = json!({
"countries": "Spain",
"cities": ["Berlin"],
});
assert_eq!(data, serde_json::from_value(j).unwrap());
Trait Implementations
sourceimpl<'de, T, U, FORMAT> DeserializeAs<'de, Vec<T, Global>> for OneOrMany<U, FORMAT> where
U: DeserializeAs<'de, T>,
FORMAT: Format,
impl<'de, T, U, FORMAT> DeserializeAs<'de, Vec<T, Global>> for OneOrMany<U, FORMAT> where
U: DeserializeAs<'de, T>,
FORMAT: Format,
sourcefn deserialize_as<D>(deserializer: D) -> Result<Vec<T>, D::Error> where
D: Deserializer<'de>,
fn deserialize_as<D>(deserializer: D) -> Result<Vec<T>, D::Error> where
D: Deserializer<'de>,
Deserialize this value from the given Serde deserializer.
sourceimpl<T, U> SerializeAs<Vec<T, Global>> for OneOrMany<U, PreferOne> where
U: SerializeAs<T>,
impl<T, U> SerializeAs<Vec<T, Global>> for OneOrMany<U, PreferOne> where
U: SerializeAs<T>,
sourcefn serialize_as<S>(source: &Vec<T>, serializer: S) -> Result<S::Ok, S::Error> where
S: Serializer,
fn serialize_as<S>(source: &Vec<T>, serializer: S) -> Result<S::Ok, S::Error> where
S: Serializer,
Serialize this value into the given Serde serializer.
sourceimpl<T, U> SerializeAs<Vec<T, Global>> for OneOrMany<U, PreferMany> where
U: SerializeAs<T>,
impl<T, U> SerializeAs<Vec<T, Global>> for OneOrMany<U, PreferMany> where
U: SerializeAs<T>,
sourcefn serialize_as<S>(source: &Vec<T>, serializer: S) -> Result<S::Ok, S::Error> where
S: Serializer,
fn serialize_as<S>(source: &Vec<T>, serializer: S) -> Result<S::Ok, S::Error> where
S: Serializer,
Serialize this value into the given Serde serializer.
impl<T: Copy, FORMAT: Copy + Format> Copy for OneOrMany<T, FORMAT>
Auto Trait Implementations
impl<T, FORMAT> RefUnwindSafe for OneOrMany<T, FORMAT> where
FORMAT: RefUnwindSafe,
T: RefUnwindSafe,
impl<T, FORMAT> Send for OneOrMany<T, FORMAT> where
FORMAT: Send,
T: Send,
impl<T, FORMAT> Sync for OneOrMany<T, FORMAT> where
FORMAT: Sync,
T: Sync,
impl<T, FORMAT> Unpin for OneOrMany<T, FORMAT> where
FORMAT: Unpin,
T: Unpin,
impl<T, FORMAT> UnwindSafe for OneOrMany<T, FORMAT> where
FORMAT: UnwindSafe,
T: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more