Cannot store io.to("room") in a variable

[fangzhangmnm]

You want to:

• report a bug
• request a feature

Current behaviour

When I store a io.to object to a variable, and call the object, the message was sent to all the clients, not only the clients in the room.

Steps to reproduce (if the current behaviour is a bug)

I store io.to to a variable:

this.broadcaster=io.to(this.internalRoomName);

Then I call the variable again somewhere else:

this.broadcaster.emit("someevent","something")

the server broadcast the event to all the client, not only the clients in the room

Expected behaviour

What I expected:

io.to(this.internalRoomName).emit("someevent","something")

Setup

• OS: Win10
• browser: Chrome and Edge
• socket.io version: v2.1.1

Other information (e.g. stacktraces, related issues, suggestions how to fix)

[ralphpig]

This is expected behavior.

When you call io.to(roomId), roomId is only stored for the upcoming emit(), and then those rooms are reset during emit().

So this.broadcaster = io.to(this.internalRoomName) returns the original, modified io instance, and once this.broadcaster.emit(...) is called once, the rooms you set with .to(...) are reset.

[zyf0330]

I don't think this behavior is a good design. And doc describes it ambiguous

Sets a modifier for a subsequent event emission that the event will only be broadcasted to clients that have joined the given room.

I think this sentence means this modifier works for following event emission.

[darrachequesne]

This was fixed by ac9e8ca and included in socket.io@4.0.0

Calling io.to() (or any other broadcast modifier) will now return an immutable instance:

const operator1 = io.to("room1");
const operator2 = operator1.to("room2");
const operator3 = socket.broadcast;
const operator4 = socket.to("room3").to("room4");

operator1.emit(/* ... */); // only to clients in "room1"
operator2.emit(/* ... */); // to clients in "room1" or in "room2"
operator3.emit(/* ... */); // to all clients but the sender
operator4.emit(/* ... */); // to clients in "room3" or in "room4" but the sender

Documentation: https://socket.io/docs/v3/migrating-from-3-x-to-4-0/#io-to-is-now-immutable