wait_for()

Wait for the selected event to happen before proceeding.

Method Syntax
db.wait_for(event)

Arguments

WaitFor is a simple enum with two variants representing the event to wait for.

pub enum WaitFor {
    Connection,
    Database,
}

Example usage

The following test from the source code demonstrates the behaviour of the .wait_for_() method in a variety of situations.

use std::task::Poll;

use surrealdb::engine::remote::ws::{Client, Ws};
use surrealdb::opt::auth::Root;
use surrealdb::opt::WaitFor::{Connection, Database};
use surrealdb::Surreal;

use futures::poll;
use std::pin::pin;

#[tokio::main]
async fn main() -> surrealdb::Result<()> {

    // Create an unconnected client
    // At this point wait_for should continue to wait for both the connection and database selection.
    let db: Surreal<Client> = Surreal::init();
    assert_eq!(poll!(pin!(db.wait_for(Connection))), Poll::Pending);
    assert_eq!(poll!(pin!(db.wait_for(Database))), Poll::Pending);

    // Connect to the server
    // The connection event should fire and allow wait_for to return immediately when waiting for a connection.
    // When waiting for a database to be selected, it should continue waiting.
    db.connect::<Ws>("127.0.0.1:8000").await.unwrap();
    assert_eq!(poll!(pin!(db.wait_for(Connection))), Poll::Ready(()));
    assert_eq!(poll!(pin!(db.wait_for(Database))), Poll::Pending);

    // Sign into the server
    // At this point the connection has already been established but the database hasn't been selected yet.
    db.signin(Root {
        username: "root",
        password: "root",
    })
    .await
    .unwrap();
    assert_eq!(poll!(pin!(db.wait_for(Connection))), Poll::Ready(()));
    assert_eq!(poll!(pin!(db.wait_for(Database))), Poll::Pending);

    // Selecting a namespace shouldn't fire the database selection event.
    db.use_ns("namespace").await.unwrap();
    assert_eq!(poll!(pin!(db.wait_for(Connection))), Poll::Ready(()));
    assert_eq!(poll!(pin!(db.wait_for(Database))), Poll::Pending);

    // Select the database to use
    // Both the connection and database events have fired, wait_for should return immediately for both.
    db.use_db("database").await.unwrap();
    assert_eq!(poll!(pin!(db.wait_for(Connection))), Poll::Ready(()));
    assert_eq!(poll!(pin!(db.wait_for(Database))), Poll::Ready(()));
    Ok(())
}

See also

• .wait_for() method on Docs.rs