24 lines
802 B
Markdown
24 lines
802 B
Markdown
# 订阅
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订阅根对象和其它根对象定义稍有不同，它的Resolver函数总是返回一个 [Stream](https://docs.rs/futures-core/~0.3/futures_core/stream/trait.Stream.html) 或者`Result<Stream>`，而字段参数通常作为数据的筛选条件。
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下面的例子订阅一个整数流，它每秒产生一个整数，参数`step`指定了整数的步长，默认为1。
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```rust
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use async_graphql::*;
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struct Subscription;
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#[Subscription]
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impl Subscription {
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async fn integers(&self, #[graphql(default = 1)] step: i32) -> impl Stream<Item = i32> {
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let mut value = 0;
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tokio_stream::wrappers::IntervalStream::new(tokio::time::interval(Duration::from_secs(1)))
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.map(move |_| {
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value += step;
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value
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})
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}
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}
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```
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