# Using Moustache in Subflow fields for dynamic and explicit content?

**URL:** <https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337>\
**Category:** Core Development\
**Created:** [17 October 2021 22:37 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337 "2021-10-17T22:37:12Z")\
**Posts on this page:** 10\
**Page:** 1

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**Author:** ![JpEncausse](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpencausse/32/2561_2.png) [@JpEncausse](https://discourse.nodered.org/u/JpEncausse)\
**Post date:** [17 October 2021 22:37 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/1 "2021-10-17T22:37:12Z")

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Hello,  
(First thanks for Node-RED an amazing tool I use for personal project for 5 years)

I love default nodes and subflow mechanism, but I struggle on the same issues/pattern :  
[a Function Node to Set msg.val.ues] =\> [a stand node like HTTP or Subflow]

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/7/e/7e738de913c0d0091fc47d98e6231966935aa809.png)

I'd love to remove this "glue" to chain only my subflows but I don't understand how I could use dynamic variable from msg.\* into my subflow ?

I give a try to Moustache like HTTP Node but it doesn't work:

![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/5/2/522255e43a79034584a26b2e72950708175ab5ae.png)

What is the best practice ?At the moment I do `env.get('my-var') || msg['my-var']` but I still have to prepare msg['my-var'].

- Is there a way to run Moustache on `env.get('my-var')` ?
- Or should I call setMessageProperty() on it ?
- Or have msg. field type in subflow (but I understand it's static)
- Or expression field type (and do $string(payload[my-var])

I think it's more readable to explicitly set in the subflow instance my data is in msg.x.y than read it magically from msg object.

Many Thanks !

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<div class="post-metadata">

**Author:** ![bakman2](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bakman2/32/6207_2.png) [@bakman2](https://discourse.nodered.org/u/bakman2)\
**Post date:** [18 October 2021 05:41 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/2 "2021-10-18T05:41:59Z")

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~~You can use a template node. [See documentation](https://nodered.org/docs/user-guide/nodes#template).~~

Maybe I am misunderstanding what you are trying to accomplish. There is a documentation section about [environment variables](https://nodered.org/docs/user-guide/environment-variables).

Note that these are only expanded once, upon deploy. It behaves like a "replace this with this" it is not "dynamic".

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<div class="post-metadata">

**Author:** ![JpEncausse](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpencausse/32/2561_2.png) [@JpEncausse](https://discourse.nodered.org/u/JpEncausse)\
**Post date:** [18 October 2021 09:48 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/3 "2021-10-18T09:48:09Z")

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Let me explain an other way :

- A subflow can only have static variable (string, int, env, etc ...) set as env
- A subflow have acces to "msg" from flow

If I design a generic sublow like a FaceRecognition subflow (that only do a REST request).

- I don't want to use in my subflow `msg.my-parameter` because in my master flow I would have to setup `msg.my-parameter` in a Function or Change node.
- I'd love a [msg.] field in my subflow to gather the right data in my master flow
- or a [string] field (my subflow will do the eval() or getMessageProperty()
- or something else dynamic

The only issue I have with Node-RED is there is too many Function node to glue things together. Sometimes, often, that's not required if we could use subflow fields.

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<div class="post-metadata">

**Author:** ![E1cid](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/e1cid/32/77971_2.png) [@E1cid](https://discourse.nodered.org/u/E1cid)\
**Post date:** [18 October 2021 10:23 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/4 "2021-10-18T10:23:45Z")

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You can set up a string field to reference the incoming msg property you would like to use in the subflow. So when you use a new copy of the subflow you just type the msg property you want the subflow to use.  
e.g.

```auto
[{"id":"43d574be.4067ac","type":"subflow","name":"Subflow 1","info":"","category":"","in":[{"x":160,"y":140,"wires":[{"id":"7665008.a988d"}]}],"out":[{"x":460,"y":160,"wires":[{"id":"7665008.a988d","port":0}]}],"env":[{"name":"msg_in","type":"str","value":"normal","ui":{"type":"input","opts":{"types":["str"]}}}],"color":"#DDAA99"},{"id":"7665008.a988d","type":"function","z":"43d574be.4067ac","name":"","func":"let msg_in = msg[env.get(\"msg_in\")];\nmsg.payload = msg_in\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":320,"y":160,"wires":[[]]},{"id":"18f08d85.db084a","type":"inject","z":"b779de97.b1b46","name":"","props":[{"p":"normal","v":"{\"test\":1}","vt":"json"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":160,"y":4600,"wires":[["c233f4f0.d42cb8"]]},{"id":"c233f4f0.d42cb8","type":"subflow:43d574be.4067ac","z":"b779de97.b1b46","name":"","env":[],"x":380,"y":4600,"wires":[["ae4ef9b4.4bd328"]]},{"id":"ae4ef9b4.4bd328","type":"debug","z":"b779de97.b1b46","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":630,"y":4420,"wires":[]},{"id":"6339434e.0dcb24","type":"subflow:43d574be.4067ac","z":"b779de97.b1b46","name":"","env":[{"name":"msg_in","value":"another","type":"str"}],"x":380,"y":4660,"wires":[["ae4ef9b4.4bd328"]]},{"id":"124399ec.8baf5e","type":"inject","z":"b779de97.b1b46","name":"","props":[{"p":"another","v":"{\"test\":2}","vt":"json"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":163.3333282470703,"y":4654.33349609375,"wires":[["6339434e.0dcb24"]]}]

```

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<div class="post-metadata">

**Author:** ![JpEncausse](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpencausse/32/2561_2.png) [@JpEncausse](https://discourse.nodered.org/u/JpEncausse)\
**Post date:** [18 October 2021 10:57 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/5 "2021-10-18T10:57:36Z")

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Yes that's what I did :  
`RED.util.getMessageProperty(msg, env.get('env-debug-str'))`

I rather like `getMessageProperty()` because it handle deep syntaxe. But it's not perfect because it's hard to detect if it's a real string (static value) or a msg.\*\*\* string. I don't understand why there is no `msg.*` field type for subflow ?

The other issue is payload, I use to build a payload for an HTTP Request in a Function Node:

```auto
msg.payload = {
    'name' : msg.FacePerson.fields.Name,
    'userData' : msg.FacePerson.fields.UserData
}

```

That's something that would be really cool to do in a JSON field instead of using a change node before. It's just mixing / reorganizing stuff

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<div class="post-metadata">

**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:** [18 October 2021 11:48 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/6 "2021-10-18T11:48:30Z")

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> [@JpEncausse](#):
>
> I don't understand why there is no `msg.*` field type for subflow ?

Because Subflow properties are not dynamic. They are evaluated when the flow is deployed and their values cannot change.

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<div class="post-metadata">

**Author:** ![JpEncausse](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpencausse/32/2561_2.png) [@JpEncausse](https://discourse.nodered.org/u/JpEncausse)\
**Post date:** [18 October 2021 11:56 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/7 "2021-10-18T11:56:39Z")

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Yes that what I understand reading other messages. And I assume you can't run a `RED.util.getMessageProperty(msg, env.get('env-debug-str'))` when calling the node because env vars are imutable.

My best bet is to write a `CUSTOM.getMessageProperty(msg, prop)` that wrap `getMessageProperty`, try/catch errors and return the prop itself if there is results. For each of my subflow's fields

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<div class="post-metadata">

**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:** [18 October 2021 11:59 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/8 "2021-10-18T11:59:04Z")

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> [@JpEncausse](#):
>
> The other issue is payload, I use to build a payload for an HTTP Request in a Function Node:
> 
> ```auto
> msg.payload = {
> 'name' : msg.FacePerson.fields.Name,
> 'userData' : msg.FacePerson.fields.UserData
> }
> 
> ```
> 
> That's something that would be really cool to do in a JSON field instead of using a change node before. It's just mixing / reorganizing stuff

You can do that with the Template node, configured to parse the result as JSON.

---

<div class="post-metadata">

**Author:** ![JpEncausse](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/jpencausse/32/2561_2.png) [@JpEncausse](https://discourse.nodered.org/u/JpEncausse)\
**Post date:** [18 October 2021 12:22 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/9 "2021-10-18T12:22:15Z")

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Yes there is many ways to do that Function, Template, Change node, etc ...  
I try to improve readability of my flow, and remove cluster of [Node doing configuration] + [Node doing] actions.

I'm proud of that one that send "chat messages" to a smart mirror :

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/c/4/c4bec462728ebb1056e452e8a542735272fe4b6c.png)

But not happy with that one that send action to the smart mirror :  
 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/0/3/036fda5a3ae214311cd0ce5ac7832dba4cc4b3dc.png)

(Yes function node can be replaced by something else), but for an elegant / readable flow it's just a matter of picking fields from the msg.\* most of the time

(BTW I love current subflow fields added in Node-RED compared to previous version it's a game changer, thanks !)

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [17 December 2021 12:22 UTC](https://discourse.nodered.org/t/using-moustache-in-subflow-fields-for-dynamic-and-explicit-content/52337/10 "2021-12-17T12:22:22Z")

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