Struct serde_with::DefaultOnNull [−][src]
pub struct DefaultOnNull<T = Same>(_);
Expand description
Deserialize Default
from null
values
Instead of erroring on null
values, it simply deserializes the Default
variant of the type.
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_null
compatible with serde’s with-annotation.
Examples
#[serde_as]
#[derive(Deserialize, Debug)]
struct A {
#[serde_as(deserialize_as = "DefaultOnNull")]
value: u32,
}
let a: A = serde_json::from_str(r#"{"value": 123}"#).unwrap();
assert_eq!(123, a.value);
// null values are deserialized into the default, here 0
let a: A = serde_json::from_str(r#"{"value": null}"#).unwrap();
assert_eq!(0, a.value);
DefaultOnNull
can be combined with other conversion methods.
In this example we deserialize a Vec
, each element is deserialized from a string.
If we encounter null, then we get the default value of 0.
#[serde_as]
#[derive(Serialize, Deserialize)]
struct C {
#[serde_as(as = "Vec<DefaultOnNull<DisplayFromStr>>")]
value: Vec<u32>,
};
let c: C = serde_json::from_value(json!({
"value": ["1", "2", null, null, "5"]
})).unwrap();
assert_eq!(vec![1, 2, 0, 0, 5], c.value);
Trait Implementations
Returns the “default value” for a type. Read more
impl<'de, T, U> DeserializeAs<'de, T> for DefaultOnNull<U> where
U: DeserializeAs<'de, T>,
T: Default,
impl<'de, T, U> DeserializeAs<'de, T> for DefaultOnNull<U> where
U: DeserializeAs<'de, T>,
T: Default,
Deserialize this value from the given Serde deserializer.
Serialize this value into the given Serde serializer.
Auto Trait Implementations
impl<T> RefUnwindSafe for DefaultOnNull<T> where
T: RefUnwindSafe,
impl<T> Send for DefaultOnNull<T> where
T: Send,
impl<T> Sync for DefaultOnNull<T> where
T: Sync,
impl<T> Unpin for DefaultOnNull<T> where
T: Unpin,
impl<T> UnwindSafe for DefaultOnNull<T> where
T: UnwindSafe,
Blanket Implementations
Mutably borrows from an owned value. Read more