Struct serde_with::OneOrMany [−][src]
Expand description
Deserialize one or many elements
Sometime it is desireable 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
impl<'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,
Deserialize this value from the given Serde deserializer.
fn 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.
fn 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.
Auto Trait Implementations
impl<T, FORMAT> RefUnwindSafe for OneOrMany<T, FORMAT> where
FORMAT: RefUnwindSafe,
T: RefUnwindSafe,
impl<T, FORMAT> UnwindSafe for OneOrMany<T, FORMAT> where
FORMAT: UnwindSafe,
T: UnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more