# Type error: RED.comms.subscribe

**URL:** <https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957>\
**Category:** Developing Nodes\
**Created:** [13 September 2024 16:32 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957 "2024-09-13T16:32:18Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![jpadie](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpadie/32/87036_2.png) [@jpadie](https://discourse.nodered.org/u/jpadie)\
**Post date:** [13 September 2024 16:32 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/1 "2024-09-13T16:32:19Z")

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Hello  
I am getting an error that  
`Property 'subscribe' does not exist on type 'NodeAPIComms'.`  
when trying to subscribe to notifications.  
` RED.comms.subscribe("notification/#", (topic, payload) => {`

looking at the types file I can see there is only a definition for the publish property.

Can anyone shed any light on this? The readme suggests the last update to the types file was 8th March 2024.

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**Author:** ![knolleary](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/knolleary/32/3_2.png) [@knolleary](https://discourse.nodered.org/u/knolleary)\
**Post date:** [13 September 2024 16:36 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/2 "2024-09-13T16:36:35Z")

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Hi,

The Types aren't maintained by the Node-RED project, so I cannot vouch for their accuracy.

Where exactly are you trying to use that? Is that in the backend (the .js part of your node) or the frontend (the .html part of your node)?

Can you explain why you want to subscribe to notifications? They are an internal event between the runtime and editor. `RED.comms` isn't a public API we have documented for nodes to use - so it may not be the right thing for you to be using.

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<div class="post-metadata">

**Author:** ![jpadie](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpadie/32/87036_2.png) [@jpadie](https://discourse.nodered.org/u/jpadie)\
**Post date:** [13 September 2024 17:01 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/3 "2024-09-13T17:01:56Z")

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sure - perhaps there is another way to skin the proverbial cat.

I'm developing a node-red interface to matter, leveraging @Apollon77's work on matter.js.

the config node represents the matter server and aggregator.

each synthetic device should wait until the matter server (and aggregator) have been successfully brought on line before registering themselves against the aggregator.

My approach so far has been something like this:

`emit("matterAggregatorStarted", matterAggregator)`

but in testing I am seeing the logs start complaining about the number of listeners on this event. Not knowing any better, perhaps, I followed the advice [here](https://www.prescientdevices.com/blog/how-to-communicate-between-node-red-editor-and-node-red-runtime#runtime) to create pubsub type behaviours.

Is there a better/more standardised way of runtime nodes listening for an internal trigger before they do something?

many thanks  
Justin

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<div class="post-metadata">

**Author:** ![marcus-j-davies](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/marcus-j-davies/32/103435_2.png) [@marcus-j-davies](https://discourse.nodered.org/u/marcus-j-davies)\
**Post date:** [13 September 2024 17:41 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/4 "2024-09-13T17:41:13Z")

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Hi @jpadie

If you want to alert your nodes that something has initialised.  
a way you should approach this (and one I use is as follows)

In your - lets call them `client` nodes to the `config` node.

Add a method to your `config` node

```auto
this.registerClient = (NodeID, callback) => {
   // Store callback referenced by the Node ID
}

```

In your `client` nodes

```auto
this.MyCallback = (event, body) => {
  // do magic
}

this.config.registerClient(this.id,this.MyCallback)

```

Then in the `config` node (and when time is right)

```auto
this.clients.each((c) => {
  c.callback('Im Ready Baby',<some fancy thing>)
})

```

I use this pattern often - and it works well  
This doesn't use any form of signalling but more relationship driven communication

I used the word **Should** - but its just a possible way (and one that I use)

I'm pretty sure config nodes are started first - hence why this works (at least for me)

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<div class="post-metadata">

**Author:** ![jpadie](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpadie/32/87036_2.png) [@jpadie](https://discourse.nodered.org/u/jpadie)\
**Post date:** [14 September 2024 00:52 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/5 "2024-09-14T00:52:10Z")

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@marcus-j-davies  
thank you. I don't think that the idea quite works for me as the client nodes may not be instantiated at any particular moment (so when the config node iterates over the client collection it may not sweep them all up). However a minor adaptation in the config functoin should fix that and I'm very grateful for the pointer.

I will also submit a PR for the missing comms Types next week as it seems to be a mistaken omission rather than absent by design; and the comms API is documented; so worth Typing.

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<div class="post-metadata">

**Author:** ![dceejay](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/dceejay/32/38_2.png) [@dceejay](https://discourse.nodered.org/u/dceejay)\
**Post date:** [14 September 2024 06:54 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/6 "2024-09-14T06:54:53Z")

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As @knolleary said the commas api is not a public one, so should not be considered to be stable, and may change without warning. (Unlikely , but…)

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<div class="post-metadata">

**Author:** ![marcus-j-davies](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/marcus-j-davies/32/103435_2.png) [@marcus-j-davies](https://discourse.nodered.org/u/marcus-j-davies)\
**Post date:** [14 September 2024 07:20 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/7 "2024-09-14T07:20:21Z")

</div>

> [@jpadie](#):
>
> as the client nodes may not be instantiated at any particular moment

I address this by returning the state during registration (sorry I should have included that)

**Config**

```auto
this.registerClient = (NodeID, callback) => {
   // Store callback referenced by the Node ID
   return <current state>
}

```

**Client**

```auto
const currentState = this.config.registerClient(this.id,this.MyCallback)
if(currentState.ready){
     doMagic() // else doMagic() is executed on the ready event you pass via the registered callbacks
}

```

This allows late to the party `client` nodes, being advised of the current state

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [28 September 2024 07:20 UTC](https://discourse.nodered.org/t/type-error-red-comms-subscribe/90957/8 "2024-09-28T07:20:43Z")

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