# Subflows, outputs, environment variables - today's question. (Demarcation lines?)
**URL:** https://discourse.nodered.org/t/subflows-outputs-environment-variables-todays-question-demarcation-lines/59001
**Category:** General
**Created:** [26 February 2022 00:25 UTC](https://discourse.nodered.org/t/subflows-outputs-environment-variables-todays-question-demarcation-lines/59001 "2022-02-26T00:25:01Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)
#### Post date: [26 February 2022 00:25 UTC](https://discourse.nodered.org/t/subflows-outputs-environment-variables-todays-question-demarcation-lines/59001/1 "2022-02-26T00:25:01Z")
This question has popped up.
# Scenario:
A message comes in. It can be `A` or `B`.
Depending if it is `A` or `B` determines the output.
The output is (for now) `msgA` or `msgB`. Just to keep things clear for association.
# Big picture:
The message arrives and the correct message is then sent.
# Observation:
As is, the two output messages are defined.
So it is pretty simple how things work.
Taking it to a _block_ of nodes in the flow.
You can change the `msgA` and `msgB` by `flow.context` or `global.context`.
Again: Fair enough.
This allows you to change the values. (Good)
# The spanner:
Subflows are still being explored and so I am going to ask questions.
Some good. Some silly.
And I think I may have just realised the answer, but want to check.
So ok, in the building of a `subflow`, I can define `environment variables` which are used in the subflow to define things.
Like - for instance - `msgA` and `msgB`.
But only to a point.
Subflows are great as they allow you to replace duplicate code/nodes (more so) with a _single_ node.
I have a few occurrences of the subflow doing the same thing, but not quite.
Where is the _line_ drawn to what is **IN** the subflow and what is **OUTSIDE**?
(and how many outputs does it need?)
The subflows spit out their `msgA` and `msgB` messages (one output) to do their things.
So, _ideally_ that should be enough. The _downstream_ code parses the message and acts accordingly.
I have some RGB LEDs. _(Yeah, don't go there. I've had enough fun getting them working)_
The structure is this:
`rgb,(led),r,g,b`
It is text at this stage.
rgb - the _command_
(led) - a _number_ to indicate which LED.
r,g,b - values from 0 to 255.
I have LED ~~6~~ 5 assigned a job. (edited: I think you can see a problem)
If something happens, it starts flashing. This is done with a subflow and where the problem starts.
Below is an example of the subflow.
A message is received that _activates_ the subflow and it starts alternating the output message at a given speed and at the output of it are the two alternating messages.
In this example:
`rgb,5,180,0,0`
or
`rgb,5,0,0,0`
Which is fine. For now.
Then one day for what ever reason I change it and want to use LED
from `5` to `6`. _(See the problem to which I hinted above?)_
So I change the `flow.context` from `5` and change it to `6`.
That isn't going to do me much good as the output messages are fixed.
# Thoughts/Options
To get around this I could keep the output messages simple and then have a `switch` node on the output that then goes into two `change` nodes that then build the _really needed_ messages.
Again: Fair enough.
But!
Then why not have TWO outputs from the subflow - given the output messages are FIXED.
Then all I need to do is add only 2 `changed` nodes.
There is little extra overhead putting 2 outputs to the subflow and .....
# The other question:
So what _magic_ would be needed so when I define the output messages, I can include the `flow.context`.
I'm guessing it will/could be something to do with the `J:` option. But that is still WAY beyond my skill set.
I'm more asking about where the demarcation lines are to what to do.
Do I have two outputs?
Do I include the variable (to set the LED) with the inbound message?
This is (probably) page 2 stuff for most of you.
I'm stuck on page 1. 😉
I'm _spit balling_ the pros and cons of what to do.
It is just I am _(again)_ TRYING to write better code and I have a lot of machines to go over and bring their code up to speed.
While doing it these questions are presenting themselves to me and I just have no idea of their relationship with things in the bigger picture.
Sure, I **CAN** define how they interact and what the _rules_ are. I just would like to get an external perspective to make sure I'm not missing any elephants.
(I'm good at doing that)
Sorry it was so long and I hope it makes sense. I am trying (argh!) to explain it as best I can.
But not really understanding it isn't helping me do a good job on that front either.
```auto
[{"id":"ca5e1e7f2227fa14","type":"subflow","name":"Blinker","info":"2021 12 7 \nA subflow to send pulsing messages at a given interval to make something *flash*.\n\nConfigurable by setting `environment` variables in the node's settings.\n\n\n# **Output toggle node to send alternating messages at a specified frequency.** \n# \n\n## 3 things need to be set to configure this subflow\n1 - `delay`: milliseconds between toggles (override with msg.delay)\n\n2 - `msg1`: text message for state 1 \n\n3 - `msg2`: text message for state 2 \n\n`msg.topic` is output and alternates between `msg1` and `msg2` to indicate which message is being sent.\n\n## Optional:\n`offmsg` - sent when it is reset.\n\nMay be handy to make sure things are *off*.\n\n## Input message\nTo start send `msg` (anything)\n\nTo stop, send `msg.reset`","category":"","in":[{"x":50,"y":80,"wires":[{"id":"3a95f6976aee6fd0"}]}],"out":[{"x":920,"y":70,"wires":[{"id":"f3b2b2634e2662cd","port":1},{"id":"a655faf0bc379507","port":0}]}],"env":[{"name":"delay","type":"num","value":""},{"name":"msg1","type":"str","value":""},{"name":"msg2","type":"str","value":""},{"name":"offmsg","type":"str","value":""}],"meta":{"module":"Toggler","version":"0.1.1","desc":"Toggles output between `msg1` and `msg2` set in node config"},"color":"#A6BBCF","icon":"node-red-contrib-bool-gate/switch.png","status":{"x":920,"y":170,"wires":[{"id":"502c279ae9a6f385","port":0}]}},{"id":"c57d4f9cf1932087","type":"trigger","z":"ca5e1e7f2227fa14","name":"","op1":"1","op2":"0","op1type":"str","op2type":"str","duration":"-2","extend":false,"overrideDelay":true,"units":"s","reset":"","bytopic":"all","topic":"topic","outputs":1,"x":370,"y":400,"wires":[["dc59ee15636e05ce"]]},{"id":"dc59ee15636e05ce","type":"function","z":"ca5e1e7f2227fa14","name":"toggle","func":"msg1 = {};\nlet c = context.get(\"counter\") ||0;\nif (c == 0)\n{\n // 0\n //msg.payload = \"rgb,1,0,18,12\";\n msg.payload = env.get(\"msg1\");\n msg.topic = \"A\";\n} else\nif (c == 1)\n{\n // 1\n //msg.payload = \"rgb,1,0,0,0\";\n msg.payload = env.get(\"msg2\");\n msg.topic = \"B\";\n}\nmsg1.payload = c;\nc = (c + 1) % 2;\ncontext.set(\"counter\",c);\nreturn [msg,msg1];","outputs":2,"noerr":0,"initialize":"","finalize":"","libs":[],"x":540,"y":400,"wires":[[],["5f212ac993db393c"]]},{"id":"cb927a5096e82c6b","type":"change","z":"ca5e1e7f2227fa14","name":"","rules":[{"t":"set","p":"delay","pt":"msg","to":"delay","tot":"env"}],"action":"","property":"","from":"","to":"","reg":false,"x":180,"y":400,"wires":[["c57d4f9cf1932087"]]},{"id":"dc53c043d49299b6","type":"switch","z":"ca5e1e7f2227fa14","name":"reset?","property":"reset","propertyType":"msg","rules":[{"t":"nnull"}],"checkall":"true","repair":false,"outputs":1,"x":150,"y":440,"wires":[["7cb7dddb4ea4f5d5","06acc957025d15a9"]]},{"id":"7cb7dddb4ea4f5d5","type":"switch","z":"ca5e1e7f2227fa14","name":"off msg?","property":"offmsg","propertyType":"env","rules":[{"t":"nempty"}],"checkall":"true","repair":false,"outputs":1,"x":350,"y":440,"wires":[["f46b5eab2fed46bc"]]},{"id":"f46b5eab2fed46bc","type":"change","z":"ca5e1e7f2227fa14","name":"set off message","rules":[{"t":"set","p":"payload","pt":"msg","to":"offmsg","tot":"env"}],"action":"","property":"","from":"","to":"","reg":false,"x":510,"y":440,"wires":[[]]},{"id":"5f212ac993db393c","type":"function","z":"ca5e1e7f2227fa14","name":"","func":"let c = msg.payload;\nif (c == 0)\n{\n msg.payload = ({text: \"A\"});\n} else if (c == 1)\n{\n msg.payload = ({text: \"B\"});\n} else\n msg.payload = ({text:\" \"});\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":540,"y":500,"wires":[[]]},{"id":"06acc957025d15a9","type":"change","z":"ca5e1e7f2227fa14","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"reset","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":315,"y":500,"wires":[["5f212ac993db393c"]],"l":false},{"id":"c53ebcc9e62a7552","type":"trigger","z":"ca5e1e7f2227fa14","name":"resend every x","op1":"1","op2":"0","op1type":"str","op2type":"str","duration":"-1","extend":false,"overrideDelay":true,"units":"s","reset":"","bytopic":"all","topic":"topic","outputs":1,"x":430,"y":80,"wires":[["f3b2b2634e2662cd"]]},{"id":"f3b2b2634e2662cd","type":"function","z":"ca5e1e7f2227fa14","name":"toggle","func":"delete msg.delay;\nconst msg1 = {};\nlet c = context.get(\"counter\") ||0;\n\nif (c == 0) {\n // 0\n msg.payload = env.get(\"msg1\");\n msg.topic = \"msg1\";\n} else if (c == 1) {\n // 1\n msg.payload = env.get(\"msg2\");\n msg.topic = \"msg2\";\n};\n\nmsg1.payload = c;\nc = (c + 1) % 2;\ncontext.set(\"counter\",c);\nreturn [msg1,msg];","outputs":2,"noerr":0,"initialize":"","finalize":"","libs":[],"x":600,"y":80,"wires":[["502c279ae9a6f385"],[]]},{"id":"c183245c1a6a7fac","type":"switch","z":"ca5e1e7f2227fa14","name":"is reset?","property":"reset","propertyType":"msg","rules":[{"t":"nnull"}],"checkall":"true","repair":false,"outputs":1,"x":410,"y":170,"wires":[["a9be61803cd67654","6e3a0cdb44f6a994"]]},{"id":"a9be61803cd67654","type":"switch","z":"ca5e1e7f2227fa14","name":"off msg?","property":"offmsg","propertyType":"env","rules":[{"t":"nempty"}],"checkall":"true","repair":false,"outputs":1,"x":610,"y":130,"wires":[["a655faf0bc379507"]]},{"id":"a655faf0bc379507","type":"change","z":"ca5e1e7f2227fa14","name":"set off message","rules":[{"t":"set","p":"payload","pt":"msg","to":"offmsg","tot":"env"},{"t":"delete","p":"reset","pt":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":790,"y":130,"wires":[[]]},{"id":"502c279ae9a6f385","type":"function","z":"ca5e1e7f2227fa14","name":"status","func":"const c = msg.payload;\n\nif (c == 0) {\n msg.payload = ({text: \"msg1\"});\n} else if (c == 1) {\n msg.payload = ({text: \"msg2\"});\n} else {\n msg.payload = ({text:\"\"});\n};\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":760,"y":170,"wires":[[]]},{"id":"6e3a0cdb44f6a994","type":"change","z":"ca5e1e7f2227fa14","name":"reset","rules":[{"t":"set","p":"payload","pt":"msg","to":"2","tot":"num"}],"action":"","property":"","from":"","to":"","reg":false,"x":600,"y":170,"wires":[["502c279ae9a6f385"]]},{"id":"3a95f6976aee6fd0","type":"function","z":"ca5e1e7f2227fa14","name":"set msg.delay","func":"msg.delay = msg.delay || env.get(\"delay\") || 1000;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":230,"y":80,"wires":[["c53ebcc9e62a7552","c183245c1a6a7fac"]]},{"id":"fe628d897122513b","type":"subflow:ca5e1e7f2227fa14","z":"f4651491.221e58","name":"New IP address","env":[{"name":"delay","value":"1300","type":"num"},{"name":"msg1","value":"rgb,5,180,0,0","type":"str"},{"name":"msg2","value":"rgb,5,0,0,0","type":"str"},{"name":"offmsg","value":"rgb,5,0,0,0","type":"str"}],"x":900,"y":2740,"wires":[["8fad71e3fdab2d59","2cedd9617f803817"]]}]
```
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [27 April 2022 00:25 UTC](https://discourse.nodered.org/t/subflows-outputs-environment-variables-todays-question-demarcation-lines/59001/2 "2022-04-27T00:25:12Z")
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