node-red-contrib-boolean-logic

Node-RED nodes to easily perform boolean logic.

##The problem Node-RED does not support multiple inputs on nodes, and it has been discussed at length in this thread. The TL;DR - as I understand it - is that the developers of NR argue that multiple inputs makes it too complex for users without a background in electrical engineering and that it is preferred users of NR instead use other means to create the desired logic (i.e. write Javascript in function-nodes).

##A solution I really needed a simple and reusable way to perform boolean logic on multiple topics without the need to write the same code over and over.

Could this be solved using a subflow? No, function-node within a subflow cannot be configured on an instance basis which is required as the logic must know how many inputs it is expecting when performing operations such as A || B or A && (B || C). Yes, that could be hard coded, but then it would not be reusable. Also, a subflow cannot use the status indicator which is a great help to the user.

What I came up with are the following nodes.

• BooleanLogic: Can perform AND, OR and XOR operations on msg.payload on any number of topics.
• Invert: Inverts the msg.payload, e.g. true -> false.
• Debug: A debug node that displays the status direcly in the editor, making it easier to see the boolean value at a specific point.

All nodes attempts to convert the incoming msg.payload to a boolean value according to these rules:

• Boolean values are taken as-is.
• For numbers, 0 evaluates to false, all other numbers evaluates to true.
• Strings are converted to numbers if they match the format of a decimal value, then the same rule as for numbers are applied. If it does not match, it evaluates to false. Also, the string "true" evaluates to true.

####BooleanLogic This node must be configured with the expected number of topics. It will not output a value until it has received the configured number of topics. Also, if it receives more than the configured number of topics it will reset (but not output a value) and wait until it once again sees the configured number of topics.

##Example

##Version history

• 0.0.1 First release
• 0.0.2
  • Changed status indicators from dot to rings for false-values.
  • Reworked the conversion of input values to be consistent between numbers and strings with numeric meaning.