1.5 KiB
1.5 KiB
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。
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。
下面是一个简单的获取连续整数的数据源:
use async_graphql::*;
use async_graphql::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.append(
(start..end).into_iter().map(|n|
Ok(Edge::new_with_additional_fields(n, n as i32, EmptyFields)),
))?;
Ok(connection)
})
}
}