Add example for connection::query

src/types/connection/mod.rs

@@ -171,6 +171,76 @@ pub trait DataSource {
 }
 
 /// If you don't want to implement DataSource, you can also use this function to query data directly.
+///
+/// # Examples
+///
+/// ```rust
+/// use async_graphql::*;
+/// use async_graphql::connection::*;
+///
+/// struct QueryRoot;
+///
+/// struct Numbers;
+///
+/// #[SimpleObject]
+/// struct Diff {
+///     diff: i32,
+/// }
+///
+/// #[Object]
+/// impl QueryRoot {
+///     async fn numbers(&self,
+///         after: Option<String>,
+///         before: Option<String>,
+///         first: Option<i32>,
+///         last: Option<i32>
+///     ) -> FieldResult<Connection<usize, i32, EmptyFields, Diff>> {
+///         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|
+///                     Edge::with_additional_fields(n, n as i32, Diff{ diff: (10000 - n) as i32 })),
+///             );
+///             Ok(connection)
+///         }).await
+///     }
+/// }
+///
+/// #[async_std::main]
+/// async fn main() {
+///     let schema = Schema::new(QueryRoot, EmptyMutation, EmptySubscription);
+///
+///     assert_eq!(schema.execute("{ numbers(first: 2) { edges { node diff } } }").await.unwrap().data, serde_json::json!({
+///         "numbers": {
+///             "edges": [
+///                 {"node": 0, "diff": 10000},
+///                 {"node": 1, "diff": 9999},
+///             ]
+///         },
+///     }));
+///
+///     assert_eq!(schema.execute("{ numbers(last: 2) { edges { node diff } } }").await.unwrap().data, serde_json::json!({
+///         "numbers": {
+///             "edges": [
+///                 {"node": 9998, "diff": 2},
+///                 {"node": 9999, "diff": 1},
+///             ]
+///         },
+///     }));
+/// }
+/// ```
 pub async fn query<Cursor, Node, ConnectionFields, EdgeFields, F, R>(
     after: Option<String>,
     before: Option<String>,