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`.subscribe()`

Subscribe the requesting client socket to changes/deletions of one or more database records.

Something.subscribe(req, ids);

Usage

	Argument	Type	Details
1	req		The incoming socket request (`req`) containing the socket to subscribe.
2	ids		An array of record ids (primary key values).

When a client socket is subscribed to a record, it is a member of its dynamic "record room". That means it will receive all messages broadcasted to that room by .publish().

Example

On the server, in a controller action:

// On the server:

if (!this.req.isSocket) {
  throw {badRequest: 'Only a client socket can subscribe to Louies.  But you look like an HTTP request to me.'};
}

// Let's say our client socket has a problem with people named "louie".

// First we'll find all users named "louie" (or "louis" even-- we should be thorough)
let usersNamedLouie = await User.find({ or: [{name: 'louie'},{name: 'louis'}] });

// Now we'll subscribe our client socket to each of these records.
User.subscribe(this.req, _.pluck(usersNamedLouie, 'id'));

// All done!  We might send down some data, or just an empty 200 (OK) response.

Then, back in our client-side code:

// On the client:

// Send a request to the "subscribeToLouies" action, subscribing this client socket
// to all future events that the server publishes about Louies.
io.socket.get('/foo/bar/subscribeToLouies', function (data, jwr){
  if (jwr.error) {
    console.error('Could not subscribe to Louie-related notifications: '+jwr.error);
    return;
  }

  console.log('Successfully subscribed.');

});

From now on, as long as our requesting client socket stays connected, it will receive a notification any time our server-side code (e.g. other actions or helpers) calls User.publish() for one of the Louies we subscribed to above.

In order for our client-side code to handle these future notifications, it must listen for the relevant event with .on(). For example:

// On the client:

// Whenever a `user` event is received, say something.
io.socket.on('user', function(msg) {
  console.log('Got a message about a Louie: ', msg);
});

See Concepts > Realtime for more background on the difference between rooms and events in Sails/Socket.IO.

Multiple rooms per record

For some applications, you may find yourself needing to manage two different channels related to the same record. To accomplish this, you can combine .getRoomName() and sails.sockets.join():

// On the server, in your subscribe action…

if (!orgId) { throw 'badRequest'; }

if (!this.req.isSocket) { throw {badRequest: 'This action is designed for use with WebSockets.'}; }

let me = await User.findOne({
  id: this.req.session.userId
})
.populate('globalAdminOfOrganizations');

// Subscribe to general notifications.
Organization.subscribe(this.req, orgId);

// If this user is a global admin of this organization, then also subscribe them to
// an additional private room (this is used for additional notifications intended only
// for global admins):
if (globalAdminOfOrganizations.includes(orgId)) {
  let privateRoom = Organization.getRoomName(`${orgId}-admins-only`);
  sails.sockets.join(this.req, privateRoom);
}

Later, to publish to one of these rooms, just compute the appropriate room name (e.g. "13-admins-only") and use sails.sockets.broadcast() to blast out your notification.

Notes

Be sure and check req.isSocket === true before passing in req to refer to the requesting socket. The provided req must be from a socket request, not just any old HTTP request.

.subscribe() will only work with requests made over a Socket.IO connection (e.g. using io.socket.get()), not over an HTTP connection (e.g. using jQuery.get()). See the sails.io.js socket client documentation for information on using client sockets to send WebSockets/Socket.IO messages with Sails.

This function does not actually talk to the database! In fact, none of the resourceful PubSub methods do. Rather, these make up a simplified abstraction layer built on top of the lower-level sails.sockets methods, designed to make your app cleaner and easier to debug by using conventional names for events/rooms/namespaces etc.

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Documentation

Reference

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