1.4 KiB
1.4 KiB
Custom scalars
In Async-graphql
most common scalar types are built in, but you can also create your own scalar types.
Using async-graphql::Scalar
, you can add support for a scalar when you implement it. You only need to implement parsing and output functions.
The following example defines a 64-bit integer scalar where its input and output are strings. (Note: Async-graphql
already supports 64-bit integers and uses strings as input and output.)
use async_graphql::*;
struct StringNumber(i64);
#[Scalar]
impl ScalarType for StringNumber {
fn parse(value: Value) -> InputValueResult<Self> {
if let Value::String(value) = &value {
// Parse the integer value
Ok(value.parse().map(StringNumber)?)
} else {
// If the type does not match
Err(InputValueError::expected_type(value))
}
}
fn to_value(&self) -> Value {
Value::String(self.0.to_string())
}
}
Use scalar!
macro to define scalar
If your type implemented serde::Serialize
and serde::Deserialize
, then you can use this macro to define a scalar more simply.
#[derive(Serialize, Deserialize)]
struct MyValue {
a: i32,
b: HashMap<String, i32>,
}
scalar!(MyValue);
// Rename to `MV`.
// scalar!(MyValue, "MV");
// Rename to `MV` and add description.
// scalar!(MyValue, "MV", "This is my value");