Struct serde_with::DefaultOnError [−][src]
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.
The same functionality is also available as serde_with::rust::default_on_error
compatible with serde’s with-annotation.
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
Returns the “default value” for a type. Read more
impl<'de, T, TAs> DeserializeAs<'de, T> for DefaultOnError<TAs> where
TAs: DeserializeAs<'de, T>,
T: Default,
[src]
impl<'de, T, TAs> DeserializeAs<'de, T> for DefaultOnError<TAs> where
TAs: DeserializeAs<'de, T>,
T: Default,
[src]Deserialize this value from the given Serde deserializer.
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
Mutably borrows from an owned value. Read more