Struct DefaultOnNull

pub struct DefaultOnNull<T = Same>(/* private fields */);

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.

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

impl<'de, T, U> DeserializeAs<'de, T> for DefaultOnNull<U>

where U: DeserializeAs<'de, T>, T: Default,

fn deserialize_as<D>(deserializer: D) -> Result<T, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T, TA> JsonSchemaAs<T> for DefaultOnNull<TA>

where TA: JsonSchemaAs<T>,

Available on crate feature schemars_0_8 only.

fn schema_name() -> String

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(gen: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn is_referenceable() -> bool

Whether JSON Schemas generated for this type should be re-used where possible using the $ref keyword.

impl<T, U> SerializeAs<T> for DefaultOnNull<U>

where U: SerializeAs<T>,

fn serialize_as<S>(source: &T, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.