67 lines
1.9 KiB
Markdown
67 lines
1.9 KiB
Markdown
# 接口(Interface)
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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Resolver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。
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`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`。
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接口字段的`name`属性表示转发的Resolver函数，并且它将被转换为驼峰命名作为字段名称。
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如果你需要自定义GraphQL接口字段名称，可以同时使用`name`和`method`属性。
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- 当`name`和`method`属性同时存在时，`name`是GraphQL接口字段名，而`method`是Resolver函数名。
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- 当只有`name`存在时, 转换为驼峰命名后的`name`是GraphQL接口字段名，而`name`是Resolver函数名。
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```rust
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use async_graphql::*;
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struct Circle {
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radius: f32,
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}
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#[Object]
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impl Circle {
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async fn area(&self) -> f32 {
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std::f32::consts::PI * self.radius * self.radius
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}
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async fn scale(&self, s: f32) -> Shape {
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Circle { radius: self.radius * s }.into()
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}
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#[field(name = "short_description")]
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async fn short_description(&self) -> String {
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"Circle".to_string()
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}
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}
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struct Square {
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width: f32,
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}
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#[Object]
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impl Square {
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async fn area(&self) -> f32 {
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self.width * self.width
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}
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async fn scale(&self, s: f32) -> Shape {
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Square { width: self.width * s }.into()
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}
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#[field(name = "short_description")]
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async fn short_description(&self) -> String {
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"Square".to_string()
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}
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}
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#[Interface(
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field(name = "area", type = "f32"),
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field(name = "scale", type = "Shape", arg(name = "s", type = "f32"))
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field(name = "short_description", method = "short_description", type = "String")
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)]
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enum Shape {
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Circle(Circle),
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Square(Square),
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}
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```
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