1.1 KiB
1.1 KiB
接口(Interface)
接口用于抽象具有特定字段集合的对象,Async-graphql
内部实现实际上是一个包装器,包装器转发接口上定义的Resolve函数到实现该接口的对象,所以接口类型所包含的字段类型,参数都必须和实现该接口的对象完全匹配。
Async-graphql
自动实现了对象到接口的转换,把一个对象类型转换为接口类型只需要调用Into::into
。
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()
}
}
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()
}
}
#[Interface(
field(name = "area", type = "f32"),
field(name = "scale", type = "Shape", arg(name = "s", type = "f32"))
)]
enum Shape {
Circle(Circle),
Square(Square),
}