async-graphql/src/docs/interface.md

Define a GraphQL interface

See also the Book.

Macro attributes

Attribute	description	Type	Optional
name	Object name	string	Y
rename_fields	Rename all the fields according to the given case convention. The possible values are "lowercase", "UPPERCASE", "PascalCase", "camelCase", "snake_case", "SCREAMING_SNAKE_CASE".	string	Y
rename_args	Rename all the arguments according to the given case convention. The possible values are "lowercase", "UPPERCASE", "PascalCase", "camelCase", "snake_case", "SCREAMING_SNAKE_CASE".	string	Y
field	Fields of this Interface	InterfaceField	N
extends	Add fields to an entity that's defined in another service	bool	Y
visible	If false, it will not be displayed in introspection. See also the Book.	bool	Y
visible	Call the specified function. If the return value is false, it will not be displayed in introspection.	string	Y

Field attributes

Attribute	description	Type	Optional
name	Field name	string	N
type	Field type	string	N
method	Rust resolver method name. If specified, name will not be camelCased in schema definition	string	Y
desc	Field description	string	Y
deprecation	Field deprecated	bool	Y
deprecation	Field deprecation reason	string	Y
arg	Field arguments	InterfaceFieldArgument	Y
external	Mark a field as owned by another service. This allows service A to use fields from service B while also knowing at runtime the types of that field.	bool	Y
provides	Annotate the expected returned fieldset from a field on a base type that is guaranteed to be selectable by the gateway.	string	Y
requires	Annotate the required input fieldset from a base type for a resolver. It is used to develop a query plan where the required fields may not be needed by the client, but the service may need additional information from other services.	string	Y
visible	If false, it will not be displayed in introspection. See also the Book.	bool	Y
visible	Call the specified function. If the return value is false, it will not be displayed in introspection.	string	Y

Field argument attributes

Attribute	description	Type	Optional
name	Argument name	string	N
type	Argument type	string	N
desc	Argument description	string	Y
default	Use Default::default for default value	none	Y
default	Argument default value	literal	Y
default_with	Expression to generate default value	code string	Y
visible	If false, it will not be displayed in introspection. See also the Book.	bool	Y
visible	Call the specified function. If the return value is false, it will not be displayed in introspection.	string	Y
secret	Mark this field as a secret, it will not output the actual value in the log.	bool	Y

Define an interface

Define TypeA, TypeB, TypeC... Implement the MyInterface

#[derive(Interface)]
enum MyInterface {
    TypeA(TypeA),
    TypeB(TypeB),
    TypeC(TypeC),
    ...
}

Fields

The type, name, and parameter fields of the interface must exactly match the type of the implementation interface, but Result can be omitted.

use async_graphql::*;

struct TypeA {
    value: i32,
}

#[Object]
impl TypeA {
    /// Returns data borrowed from the context
    async fn value_a<'a>(&self, ctx: &'a Context<'_>) -> Result<&'a str> {
        Ok(ctx.data::<String>()?.as_str())
    }

    /// Returns data borrowed self
    async fn value_b(&self) -> &i32 {
        &self.value
    }

    /// With parameters
    async fn value_c(&self, a: i32, b: i32) -> i32 {
        a + b
    }

    /// Disabled name transformation, don't forget "method" argument in interface!
    #[graphql(name = "value_d")]
    async fn value_d(&self) -> i32 {
        &self.value + 1
    }
}

#[derive(Interface)]
#[graphql(
    field(name = "value_a", type = "&'ctx str"),
    field(name = "value_b", type = "&i32"),
    field(name = "value_c", type = "i32",
        arg(name = "a", type = "i32"),
        arg(name = "b", type = "i32")),
    field(name = "value_d", method = "value_d", type = "i32"),
)]
enum MyInterface {
    TypeA(TypeA)
}

struct Query;

#[Object]
impl Query {
    async fn type_a(&self) -> MyInterface {
        TypeA { value: 10 }.into()
    }
}

# tokio::runtime::Runtime::new().unwrap().block_on(async move {
let schema = Schema::build(Query, EmptyMutation, EmptySubscription).data("hello".to_string()).finish();
let res = schema.execute(r#"
{
    typeA {
        valueA
        valueB
        valueC(a: 3, b: 2)
        value_d
    }
}"#).await.into_result().unwrap().data;
assert_eq!(res, value!({
    "typeA": {
        "valueA": "hello",
        "valueB": 10,
        "valueC": 5,
        "value_d": 11
    }
}));
# });