Hi, this is quite a "beginner's" question but hopefully someone can help? I want to build up a "definitions" file that describes the properties for various custom DIY home automation devices. I'm thinking the best way might be some form of JSON file on disk. Should I use context, and store to dis…

@hazymat , I started out using a database for this sort of thing, storing the current state of each device and updating it at every change. Since the introduction of persistent storage, I have gone back to using a JSON file for the static information about my devices and a global variable to store st…

[image] Colin: possibly an sqlite database I would actually disagree here. As long as you need the whole thing available to Node-RED, a JSON file loaded to memory is much easier to work with and avoids the additional complexity of a database. Only if you need to query or aggregate data would…

[image] TotallyInformation: I would actually disagree here. It is possibly arguable either way in this case. Requirements such as "count the number of light circuits in a room" suggest a database approach to me. Also for the Scenes, looking up the available scenes for a particular room, ad…

[image] Colin: possibly arguable either way in this case As always :wink: [image] Colin: count the number of light circuits in a room Yes, given the data shown, this might be correct. Of course, the advantage of using JSON is that you can simply adjust to need. So that you could easil…

[image] TotallyInformation: "Light 1": { "device":"Light 1", "zone":"bedroom1", "name":"Wall Light" <=========== "fitting":"wall", "colour":"warmwhite" Missing a comma??? :grin:

Thanks for your help so far. In @TotallyInformation ’s suggestion for a json file, does anyone know how it would be possible to count the number of items (eg with a specific property like fittingtype=wall) in a JSON file? With a simple loop that reads all values and compares and counts?

if the data was stored as an array of objects like: { "payload": [{ "device": "Light 1", "zone": "bedroom1", "name": "Wall Light", "fitting": "wall", "colour": "warmwhite" }, { "device": "Light 2",…

[image] zenofmud: you could use a JSONata expression Or in JavaScript: msg.payload.filter(function(item){return item.fitting === 'wall'}).length; or msg.payload.filter(function(item){return item.zone === 'bedroom1'}).length; Not as neat as @zenofmud 's expression but usable in a function …

in sql one could do a "group by" without knowing any zone/fitting names - is this also possible in jsonata?

How to store data in JSON file in Node-RED

General

Colin 7 January 2019 07:58 2

I think that possibly an sqlite database might be a better solution for this. That is exactly what databases are designed for, storing information and then looking it up later in various ways.

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How to store data in JSON file in Node-RED

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