Struct aldrin::Handle

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pub struct Handle { /* private fields */ }

Expand description

Handle to a client.

After connecting a Client to a broker, Handles are used to interact with it. The first Handle can be acquired with Client::handle. After that, Handles can be cloned cheaply.

The Client will automatically shut down when the last Handle has been dropped.

§Examples

use aldrin::Client;

// Connect to the broker:
let client = Client::connect(async_transport).await?;

// Acquire the first handle:
let handle = client.handle().clone();

// Run the client, which consumes it and leaves only the handle for interacting with it:
tokio::spawn(client.run());

// Handles are cheap to clone:
let handle2 = handle.clone();

Implementations§

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impl Handle

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pub fn shutdown(&self)

Shuts down the client.

Shutdown happens asynchronously, in the sense that when this function returns, the Client has only been requested to shut down and not yet necessarily done so. As soon as Client::run returns, it has fully shut down.

If the Client has already shut down (due to any reason), this function will not treat that as an error. This is different than most other functions, which would return Error::Shutdown instead.

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pub async fn create_object( &self, uuid: impl Into<ObjectUuid> ) -> Result<Object, Error>

Creates a new object on the bus.

The uuid must not yet exists on the bus, or else Error::DuplicateObject will be returned. Use ObjectUuid::new_v4 to create a new random v4 UUID.

§Examples

use aldrin::Error;
use aldrin::core::ObjectUuid;
use uuid::uuid;

const OBJECT2_UUID: ObjectUuid = ObjectUuid(uuid!("6173e119-8066-4776-989b-145a5f16ed4c"));

// Create an object with a random UUID:
let object1 = handle.create_object(ObjectUuid::new_v4()).await?;

// Create an object with a fixed UUID:
let object2 = handle.create_object(OBJECT2_UUID).await?;

// Using the same UUID again will cause an error:
assert_eq!(
    handle.create_object(OBJECT2_UUID).await.unwrap_err(),
    Error::DuplicateObject,
);

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pub fn call_function<Args, T, E>( &self, service_id: ServiceId, function: u32, args: &Args ) -> Result<PendingFunctionResult<T, E>, Error>
where Args: Serialize + ?Sized, T: Deserialize, E: Deserialize,

Calls a function on a service.

The function with id function will be called with the arguments args on the service identified by service_id.

The returned value of type PendingFunctionResult is a future which will resolve to the result of the function call.

§Examples

use aldrin::core::Value;

// Call function 1 with "1 + 2 = ?" as the argument.
let result = handle.call_function::<_, u32, String>(service_id, 1, "1 + 2 = ?")?;

// Await the result. The `?` here checks for errors on the protocol level, such as a
// intermediate shutdown, or whether the function call was aborted by the callee.
let result = result.await?;

// Now, result is of type `Result<u32, String>`, directly representing the result of the
// function call.
match result {
    Ok(ok) => assert_eq!(ok, 3),
    Err(err) => panic!("Function call failed: {}.", err),
}

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pub fn call_infallible_function<Args, T>( &self, service_id: ServiceId, function: u32, args: &Args ) -> Result<PendingFunctionValue<T>, Error>
where Args: Serialize + ?Sized, T: Deserialize,

Calls an infallible function on a service.

Use this method if the called function is guaranteed to never fail. If this is not true, and the function fails, then Error::InvalidReply will be returned.

The returned value of type PendingFunctionValue is a future which will resolve to the value of the function call.

§Examples

// Call function 1 with "1 + 2 = ?" as the argument.
let result = handle.call_infallible_function::<_, u32>(service_id, 1, "1 + 2 = ?")?;

assert_eq!(result.await?, 3);

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pub fn events(&self) -> Events

Creates an Events object used to subscribe to service events.

See Events for more information and usage examples.

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pub fn emit_event<T>( &self, service_id: ServiceId, event: u32, value: &T ) -> Result<(), Error>
where T: Serialize + ?Sized,

Emits an events to subscribed clients.

The event with the id event of the service identified by service_id will be emitted with the arguments args to all subscribed clients.

Use Handle::events to subscribe to events.

§Examples

// Emit event 1 with argument "Hello, world!":
handle.emit_event(service_id, 1, "Hello, world!")?;

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pub async fn query_service_version( &self, service_id: ServiceId ) -> Result<u32, Error>

Queries the version of a service.

§Examples

use aldrin::core::{ObjectUuid, ServiceUuid};
use aldrin::Error;

let object = handle.create_object(ObjectUuid::new_v4()).await?;
let service = object.create_service(ServiceUuid::new_v4(), 2).await?;

let version = handle.query_service_version(service.id()).await;
assert_eq!(version, Ok(2));

service.destroy().await?;
let version = handle.query_service_version(service.id()).await;
assert_eq!(version, Err(Error::InvalidService));

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pub async fn create_channel_with_claimed_sender<T>( &self ) -> Result<(PendingSender<T>, UnclaimedReceiver<T>), Error>
where T: Serialize + Deserialize,

Creates a channel and automatically claims the sender.

When creating a channel, one of the two end must be claimed immediately. This function claims the sender. Use create_channel_with_claimed_receiver to claim the receiver instead.

§Examples

This example assumes that there are 2 clients, represented here by handle1 and handle2.


// Client 1 creates the channel. It then unbinds the receiver and makes it available to
// client 2. This will typically happen by returning it from a function call.
let (sender, receiver) = handle1.create_channel_with_claimed_sender().await?;
let receiver = receiver.unbind();

// Client 2 gets access to the receiver, and then binds and claims it.
let mut receiver = receiver.claim(handle2.clone(), 16).await?;

// Meanwhile, client 1 waits for the receiver to be claimed.
let mut sender = sender.established().await?;

// The channel is now fully established and client 1 can send items to client 2.
sender.send_item(&1).await?;
sender.send_item(&2).await?;
sender.send_item(&3).await?;

// Client 1 will close (or drop) the channel when it has nothing to send anymore.
sender.close().await?;

// Client 2 receives all values in order. The Result in the return values can indicate
// conversion errors when an item isn't a u32.
assert_eq!(receiver.next_item().await, Ok(Some(1)));
assert_eq!(receiver.next_item().await, Ok(Some(2)));
assert_eq!(receiver.next_item().await, Ok(Some(3)));

// Client 2 can observe that the sender has been closed by receiving None. It follows by
// also closing (or dropping) the receiver.
assert_eq!(receiver.next_item().await, Ok(None));
receiver.close().await?;

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pub async fn create_channel_with_claimed_receiver<T>( &self, capacity: u32 ) -> Result<(UnclaimedSender<T>, PendingReceiver<T>), Error>
where T: Serialize + Deserialize,

Creates a channel and automatically claims the receiver.

When creating a channel, one of the two end must be claimed immediately. This function claims the receiver. Use create_channel_with_claimed_sender to claim the sender instead.

A capacity of 0 is treated as if 1 was specificed instead.

§Examples

See create_channel_with_claimed_sender for an example.

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pub async fn sync_client(&self) -> Result<(), Error>

Synchronizes with the client.

This function ensures that all previous requests to the client have been processed. There are some occasions in which requests are sent outside of an async context, e.g. when dropping values such as Object. By synchronizing with the client, it is possible to ensure that it has processed such a non-async request.

See also sync_broker, which ensures that such requests have been processed by the broker.

§Examples

use aldrin::core::ObjectUuid;
use std::mem;

let obj = handle.create_object(ObjectUuid::new_v4()).await?;

// Dropping obj will request the client to destroy the object.
mem::drop(obj);

// Ensure the request has actually been processed by the client.
handle.sync_client().await?;

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pub async fn sync_broker(&self) -> Result<(), Error>

Synchronizes with the broker.

Certain requests such as emitting an event or sending an item on a channel don’t synchronize with the broker in the same way as e.g. creating an object does. This function can be used to ensure that such a request has been processed by the broker.

See also sync_client, which ensures only that such requests have been processed by the client.

§Examples


handle.emit_event(service.id(), 0, "Hi!")?;

// Synchronize with the broker to ensure that the event has actually been processed.
handle.sync_broker().await?;

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pub async fn create_bus_listener(&self) -> Result<BusListener, Error>

Creates a new bus listener.

Bus listeners enable monitoring the bus for events about the creation and destruction of objects and services. See BusListener for more information and usage examples.

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pub fn create_discoverer<Key>(&self) -> DiscovererBuilder<'_, Key>

Create a new DiscovererBuilder.

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pub async fn find_object<const N: usize>( &self, object: Option<ObjectUuid>, services: &[ServiceUuid; N] ) -> Result<Option<(ObjectId, [ServiceId; N])>, Error>

Find an object with a specific set of services.

If object is None, then any object that has all required services may be returned. Repeated calls to this function can return different objects.

This is a convenience function for using a Discoverer to find a single object among all current objects on the bus.

§Examples

// Create an object and 2 services to find.
let obj = client.create_object(ObjectUuid::new_v4()).await?;
let svc1 = obj.create_service(ServiceUuid::new_v4(), 0).await?;
let svc2 = obj.create_service(ServiceUuid::new_v4(), 0).await?;

// Find the object.
let (object_id, service_ids) = client
    .find_object(Some(obj.id().uuid), &[svc1.id().uuid, svc2.id().uuid])
    .await?
    .unwrap();

assert_eq!(object_id, obj.id());
assert_eq!(service_ids[0], svc1.id());
assert_eq!(service_ids[1], svc2.id());

Without specifying an ObjectUuid:

// Create 2 objects and sets of services to find.
let obj1 = client.create_object(ObjectUuid::new_v4()).await?;
let svc11 = obj1.create_service(ServiceUuid::new_v4(), 0).await?;
let svc12 = obj1.create_service(ServiceUuid::new_v4(), 0).await?;

let obj2 = client.create_object(ObjectUuid::new_v4()).await?;
let svc21 = obj2.create_service(svc11.id().uuid, 0).await?;
let svc22 = obj2.create_service(svc12.id().uuid, 0).await?;

// Find any one of the objects above.
let (object_id, service_ids) = client
    .find_object(None, &[svc11.id().uuid, svc12.id().uuid])
    .await?
    .unwrap();

assert!((object_id == obj1.id()) || (object_id == obj2.id()));
assert!((service_ids[0] == svc11.id()) || (service_ids[0] == svc21.id()));
assert!((service_ids[1] == svc12.id()) || (service_ids[1] == svc22.id()));