96 lines
1.9 KiB
Markdown
96 lines
1.9 KiB
Markdown
# 合并对象(MergedObject)
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## 为同一类型实现多次Object
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通常我们在Rust中可以为同一类型创建多个实现，但由于过程宏的限制，无法为同一个类型创建多个Object实现。例如，下面的代码将无法通过编译。
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```rust
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#[Object]
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impl MyObject {
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async fn field1(&self) -> i32 {
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todo!()
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}
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}
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#[Object]
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impl MyObject {
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async fn field2(&self) -> i32 {
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todo!()
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}
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}
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```
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用 `#[derive(MergedObject)]` 宏允许你合并多个独立的Object为一个.
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**提示:** 每个`#[Object]`需要一个唯一的名称，即使在一个`MergedObject`内，所以确保每个对象有单独的名称。
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```rust
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#[derive(Default)]
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struct UserQuery;
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#[Object]
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impl UserQuery {
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async fn users(&self) -> Vec<User> {
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todo!()
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}
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}
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#[derive(Default)]
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struct MovieQuery;
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#[Object]
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impl MovieQuery {
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async fn movies(&self) -> Vec<Movie> {
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todo!()
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}
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}
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#[derive(MergedObject, Default)]
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struct Query(UserQuery, MovieQuery);
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let schema = Schema::new(
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Query::default(),
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EmptyMutation,
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EmptySubscription
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);
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```
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> ⚠️ **合并的对象无法在Interface中使用。**
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# 合并订阅
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和`MergedObject`一样，你可以派生`MergedSubscription`来合并单独的`＃[Subscription]`块。
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像合并对象一样，每个订阅块都需要一个唯一的名称。
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```rust
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#[derive(Default)]
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struct Subscription1;
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#[Subscription]
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impl Subscription1 {
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async fn events1(&self) -> impl Stream<Item = i32> {
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futures::stream::iter(0..10)
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}
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}
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#[derive(Default)]
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struct Subscription2;
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#[Subscription]
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impl Subscription2 {
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async fn events2(&self) -> impl Stream<Item = i32> {
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futures::stream::iter(10..20)
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}
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}
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#[derive(MergedSubscription, Default)]
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struct Subscription(Subscription1, Subscription2);
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let schema = Schema::new(
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Query::default(),
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EmptyMutation,
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Subscription::default()
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);
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```
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