async-graphql/docs/zh-CN/src/cursor_connections.md

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游标连接(Cursor Connections)

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

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。

下面是一个简单的获取连续整数的数据源:

use async_graphql::*;
use async_graphql::types::connection::*;

struct Query;

#[Object]
impl Query {
    async fn numbers(&self,
        after: Option<String>,
        before: Option<String>,
        first: Option<i32>,
        last: Option<i32>,
    ) -> Result<Connection<usize, i32, EmptyFields, EmptyFields>> {
        query(after, before, first, last, |after, before, first, last| async move {
            let mut start = after.map(|after| after + 1).unwrap_or(0);
            let mut end = before.unwrap_or(10000);
            if let Some(first) = first {
                end = (start + first).min(end);
            }
            if let Some(last) = last {
                start = if last > end - start {
                     end
                } else {
                    end - last
                };
            }
            let mut connection = Connection::new(start > 0, end < 10000);
            connection.edges.extend(
                (start..end).into_iter().map(|n|
                    Ok(Edge::new_with_additional_fields(n, n as i32, EmptyFields)),
            ))?;
            Ok(connection)
        })
    }
}