Struct serde_with::DefaultOnError
source · [−]pub struct DefaultOnError<T = Same>(_);
Expand description
Deserialize value and return Default
on error
The main use case is ignoring error while deserializing.
Instead of erroring, it simply deserializes the Default
variant of the type.
It is not possible to find the error location, i.e., which field had a deserialization error, with this method.
During serialization this wrapper does nothing.
The serialization behavior of the underlying type is preserved.
The type must implement Default
for this conversion to work.
Examples
#[serde_as]
#[derive(Deserialize, Debug)]
struct A {
#[serde_as(deserialize_as = "DefaultOnError")]
value: u32,
}
let a: A = serde_json::from_str(r#"{"value": 123}"#).unwrap();
assert_eq!(123, a.value);
// null is of invalid type
let a: A = serde_json::from_str(r#"{"value": null}"#).unwrap();
assert_eq!(0, a.value);
// String is of invalid type
let a: A = serde_json::from_str(r#"{"value": "123"}"#).unwrap();
assert_eq!(0, a.value);
// Map is of invalid type
let a: A = dbg!(serde_json::from_str(r#"{"value": {}}"#)).unwrap();
assert_eq!(0, a.value);
// Missing entries still cause errors
assert!(serde_json::from_str::<A>(r#"{ }"#).is_err());
Deserializing missing values can be supported by adding the default
field attribute:
#[serde_as]
#[derive(Deserialize)]
struct B {
#[serde_as(deserialize_as = "DefaultOnError")]
#[serde(default)]
value: u32,
}
let b: B = serde_json::from_str(r#"{ }"#).unwrap();
assert_eq!(0, b.value);
DefaultOnError
can be combined with other conversion methods.
In this example, we deserialize a Vec
, each element is deserialized from a string.
If the string does not parse as a number, then we get the default value of 0.
#[serde_as]
#[derive(Serialize, Deserialize)]
struct C {
#[serde_as(as = "Vec<DefaultOnError<DisplayFromStr>>")]
value: Vec<u32>,
};
let c: C = serde_json::from_value(json!({
"value": ["1", "2", "a3", "", {}, "6"]
})).unwrap();
assert_eq!(vec![1, 2, 0, 0, 0, 6], c.value);
Trait Implementations
sourceimpl<'de, T, TAs> DeserializeAs<'de, T> for DefaultOnError<TAs> where
TAs: DeserializeAs<'de, T>,
T: Default,
impl<'de, T, TAs> DeserializeAs<'de, T> for DefaultOnError<TAs> where
TAs: DeserializeAs<'de, T>,
T: Default,
sourcefn deserialize_as<D>(deserializer: D) -> Result<T, D::Error> where
D: Deserializer<'de>,
fn deserialize_as<D>(deserializer: D) -> Result<T, D::Error> where
D: Deserializer<'de>,
Deserialize this value from the given Serde deserializer.
sourceimpl<T, TAs> SerializeAs<T> for DefaultOnError<TAs> where
TAs: SerializeAs<T>,
impl<T, TAs> SerializeAs<T> for DefaultOnError<TAs> where
TAs: SerializeAs<T>,
sourcefn serialize_as<S>(source: &T, serializer: S) -> Result<S::Ok, S::Error> where
S: Serializer,
fn serialize_as<S>(source: &T, serializer: S) -> Result<S::Ok, S::Error> where
S: Serializer,
Serialize this value into the given Serde serializer.
Auto Trait Implementations
impl<T> RefUnwindSafe for DefaultOnError<T> where
T: RefUnwindSafe,
impl<T> Send for DefaultOnError<T> where
T: Send,
impl<T> Sync for DefaultOnError<T> where
T: Sync,
impl<T> Unpin for DefaultOnError<T> where
T: Unpin,
impl<T> UnwindSafe for DefaultOnError<T> where
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