46 lines
1.6 KiB
Markdown
46 lines
1.6 KiB
Markdown
# 游标连接(Cursor Connections)
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Relay定义了一套游标连接规范，以提供一致性的分页查询方式，具体的规范文档请参考[GraphQL Cursor Connections Specification](https://facebook.github.io/relay/graphql/connections.htm)。
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在`Async-graphql`中定义一个游标连接非常简单，你只需要调用connection::query函数，并在闭包中查询数据。
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下面是一个简单的获取连续整数的数据源：
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```rust
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use async_graphql::*;
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use async_graphql::types::connection::*;
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struct Query;
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#[Object]
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impl Query {
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async fn numbers(&self,
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after: Option<String>,
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before: Option<String>,
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first: Option<i32>,
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last: Option<i32>,
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) -> Result<Connection<usize, i32, EmptyFields, EmptyFields>> {
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query(after, before, first, last, |after, before, first, last| async move {
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let mut start = after.map(|after| after + 1).unwrap_or(0);
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let mut end = before.unwrap_or(10000);
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if let Some(first) = first {
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end = (start + first).min(end);
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}
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if let Some(last) = last {
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start = if last > end - start {
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end
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} else {
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end - last
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};
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}
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let mut connection = Connection::new(start > 0, end < 10000);
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connection.edges.extend(
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(start..end).into_iter().map(|n|
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Ok(Edge::new_with_additional_fields(n, n as i32, EmptyFields)),
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))?;
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Ok(connection)
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})
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}
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}
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```
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