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.subscribe()

Subscribes the requesting client socket to one or more database records (i.e. model instances).

Usage

SomeModel.subscribe(req, ids);

-or-

SomeModel.subscribe(req, ids, contexts);

By default (if no "contexts" are provided), the client socket will receive relevant messages emitted by .publishUpdate(), .publishDestroy(), .publishAdd() and .publishRemove().

Important:

This function does not actually talk to the database! In fact, none of the resourceful pubsub methods do. These are just 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.

Argument Type Details
1 req The request object (req). You should only use this method from an action.
2 ids An array of record ids (primary keys).
3 contexts An optional array of change-type strings ("contexts"). If provided, the subscribing client socket will only receive messages involving the specified types of changes (e.g. if a "destroy" context is specified, the socket will receive notifications from publishDestroy() calls involving this record). Otherwise, if left unspecified, the socket will hear about any published events involving this record.

Note: 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.

Example

subscribeToLouies: function (req, res) {
    if (!req.isSocket) {
      return res.badRequest('Only a client socket can subscribe to Louies.  You, sir, appear to be something... _else_.');
    }

    // 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)
    User.find({ or: [{name: 'louie'},{name: 'louis'}] }).exec(function(err, usersNamedLouie){
      if (err) {
        return res.negotiate(err);
      }

      // Now we'll use the ids we found to subscribe our client socket to each of these records'
      // "destroy" context.
      User.subscribe(req, _.pluck(usersNamedLouie, 'id'), ['destroy']);

      // Now any time a user named "louie" or "louis" is destroyed, our client socket will receive
      // a notification (as long as it stays connected anyways).

      // All done!  We could send down some data, but instead we send an empty response.
      // (although we're ok telling this vengeful client socket when our users get
      //  destroyed, it seems ill-advised to send him our Louies' sensitive user data.
      //  We don't want to help this guy to hunt them down irl.)
      return res.ok();
    });
  }

Blueprints and .subscribe()

By default, the blueprint find and findOne actions will call .subscribe() to subscribe a requesting socket to all returned records. However, the blueprint update and delete actions will not cause a message to be sent to the requesting socket by default--only to the other connected sockets. This is intended to allow the caller of io.socket.update() (for example) to use the client-side SDK's callback to handle the server response separately. To force the blueprint actions to send messages to all sockets, including the requesting socket, set sails.config.blueprints.mirror to true.

What is context?

If you specify a specific context (or array of contexts) to subscribe to, you will only get messages sent in that context. For example, User.subscribe(socket, user, 'update') will cause the socket to receive messages only when publishUpdate is called for user. Subsequent calls to subscribe are cumulative, so if you called User.subscribe(socket, user, 'destroy') later with the same socket, that socket would then be subscribed to messages from both publishUpdate and publishDestroy.

You can omit context to subscribe a socket to the default contexts for that model class. The default contexts are defined by the autosubscribe property of the model class. If autosubscribe is not present, then the default contexts are update, destroy, message (for custom messages), add:* and remove:* (publishAdd and publishRemove messages for associated models).

Is something missing?

If you notice something we've missed or could be improved on, please follow this link and submit a pull request to the sails-docs repo. Once we merge it, the changes will be reflected on the website the next time it is deployed.

Reference

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