客户端库提供了取消先前的订阅请求的方法。
此过程需要与服务器进行交互，因此对于异步订阅，在取消订阅由库处理时可能会有一小段时间窗口，期间可能已经有消息到达。开发者们可以忽略这种边缘情况，因为客户端库将清理任何未处理的消息，并通知服务器该订阅已不再使用。
{% tabs %} {% tab title="Go" %}
nc, err := nats.Connect("demo.nats.io")
if err != nil {
log.Fatal(err)
}
defer nc.Close()
// Sync Subscription
sub, err := nc.SubscribeSync("updates")
if err != nil {
log.Fatal(err)
}
if err := sub.Unsubscribe(); err != nil {
log.Fatal(err)
}
// Async Subscription
sub, err = nc.Subscribe("updates", func(_ *nats.Msg) {})
if err != nil {
log.Fatal(err)
}
if err := sub.Unsubscribe(); err != nil {
log.Fatal(err)
}{% endtab %}
{% tab title="Java" %}
Connection nc = Nats.connect("nats://demo.nats.io:4222");
Dispatcher d = nc.createDispatcher((msg) -> {
String str = new String(msg.getData(), StandardCharsets.UTF_8);
System.out.println(str);
});
// Sync Subscription have an unsubscribe API
Subscription sub = nc.subscribe("updates");
sub.unsubscribe();
// Async Subscriptions on the dispatcher must unsubscribe via the dispatcher,
// not the subscription
d.subscribe("updates");
d.unsubscribe("updates");
// Close the connection
nc.close();{% endtab %}
{% tab title="JavaScript" %}
const sc = StringCodec();
// set up a subscription to process a request
const sub = nc.subscribe(createInbox(), (_err, m) => {
m.respond(sc.encode(new Date().toLocaleTimeString()));
});
// without arguments the subscription will cancel when the server receives it
// you can also specify how many messages are expected by the subscription
sub.unsubscribe();{% endtab %}
{% tab title="Python" %}
nc = NATS()
await nc.connect(servers=["nats://demo.nats.io:4222"])
future = asyncio.Future()
async def cb(msg):
nonlocal future
future.set_result(msg)
sub = await nc.subscribe("updates", cb=cb)
await nc.publish("updates", b'All is Well')
# Remove interest in subject
await sub.unsubscribe()
# Won't be received...
await nc.publish("updates", b'...'){% endtab %}
{% tab title="C#" %}
// dotnet add package NATS.Net
using NATS.Net;
await using var client = new NatsClient();
// Cancel the subscription after 10 seconds
using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
// Subscribe to the "updates" subject
// We unsubscribe when we receive the message "exit"
// or when the cancellation token is triggered.
await foreach (var msg in client.SubscribeAsync<string>("updates").WithCancellation(cts.Token))
{
Console.WriteLine($"Received: {msg.Data}");
if (msg.Data == "exit")
{
// When we exit the loop, we unsubscribe from the subject
break;
}
}
Console.WriteLine("Unsubscribed from updates");{% endtab %}
{% tab title="Ruby" %}
require 'nats/client'
require 'fiber'
NATS.start(servers:["nats://127.0.0.1:4222"]) do |nc|
Fiber.new do
f = Fiber.current
sid = nc.subscribe("time") do |msg, reply|
f.resume Time.now
end
nc.publish("time", 'What is the time?', NATS.create_inbox)
# Use the response
msg = Fiber.yield
puts "Reply: #{msg}"
nc.unsubscribe(sid)
# Won't be received
nc.publish("time", 'What is the time?', NATS.create_inbox)
end.resume
end{% endtab %}
{% tab title="C" %}
natsConnection *conn = NULL;
natsSubscription *sub = NULL;
natsStatus s = NATS_OK;
s = natsConnection_ConnectTo(&conn, NATS_DEFAULT_URL);
// Subscribe
if (s == NATS_OK)
s = natsConnection_SubscribeSync(&sub, conn, "updates");
// Unsubscribe
if (s == NATS_OK)
s = natsSubscription_Unsubscribe(sub);
(...)
// Destroy objects that were created
natsSubscription_Destroy(sub);
natsConnection_Destroy(conn);{% endtab %} {% endtabs %}