async-graphql/docs/en/src/define_interface.md

Interface

Interface is used to abstract Objects with common fields. Async-graphql implements it as a wrapper. The wrapper will forward field resolution to the Object that implements this Interface. Therefore, the Object's fields' type and arguments must match with the Interface's.

Async-graphql implements auto conversion from Object to Interface, you only need to call Into::into.

Interface field names are transformed to camelCase for the schema definition. If you need e.g. a snake_cased GraphQL field name, you can use both the name and method attributes.

• When name and method exist together, name is the GraphQL field name and the method is the resolver function name.
• When only name exists, name.to_camel_case() is the GraphQL field name and the name is the resolver function name.

use async_graphql::*;

struct Circle {
    radius: f32,
}

#[Object]
impl Circle {
    async fn area(&self) -> f32 {
        std::f32::consts::PI * self.radius * self.radius
    }

    async fn scale(&self, s: f32) -> Shape {
        Circle { radius: self.radius * s }.into()
    }

    #[field(name = "short_description")]
    async fn short_description(&self) -> String {
        "Circle".to_string()
    }
}

struct Square {
    width: f32,
}

#[Object]
impl Square {
    async fn area(&self) -> f32 {
        self.width * self.width
    }

    async fn scale(&self, s: f32) -> Shape {
        Square { width: self.width * s }.into()
    }

    #[field(name = "short_description")]
    async fn short_description(&self) -> String {
        "Square".to_string()
    }
}

#[Interface(
    field(name = "area", type = "f32"),
    field(name = "scale", type = "Shape", arg(name = "s", type = "f32"))
    field(name = "short_description", method = "short_description", type = "String")
)]
enum Shape {
    Circle(Circle),
    Square(Square),
}