Flow that makes a new flow

README.md

This flow injects a JSON object with some configuration parameters:

MQTT broker address, input topic. output topic, transformation

and generates (in the debug window) the JSON for a message flow comprising:

• an MQTT input node, connected to the specified broker and subscribing to the input topic
• a function node containing the transformation code specified
• an MQTT output node, publishing to the specified output topic.

Select the JSON from the debug window, right-mouse Copy and then Import from... clipboard in Node-RED and ctrl-V the content into the text box. Click OK and the three-node flow will appear under the cursor to be parked on the worksheet.

Sample input:

{ "broker": "localhost", "input": "source_topic", "output": "destination_topic", "process": "msg.payload = "* "+msg.payload+" *";\nreturn msg;" }

(remember to escape any quotes in the "process" string!)

See my blog post about it: http://eightbar.co.uk/2014/01/19/node-red-flows-that-make-flows/

flow.json

[{"id":"278fa0eb.43aed8","type":"function","name":"broker def node","func":"// pass in: msg.parameters.broker\n\nnode_type = \"mqtt-broker\";\nmsg.id = msg.id + 1;\n\nmsg.payload.push({\n        id: msg.id,\n        type: node_type,\n        broker: msg.parameters.broker,\n        port: \"1883\"\n      });\n\n// store the broker def ID so we can refer to it in the output node\nmsg.defs = {broker: msg.id,\n \t\t\t// how far apart are nodes horizontally\n     \t \tspacing: 150}; \n\n\nreturn msg;","outputs":1,"x":441,"y":191,"z":"911370d8.e61a48","wires":[["15e5103c.e73b7"]]},{"id":"da8f9fca.854188","type":"inject","name":"parameters","topic":"","payload":"{\"broker\":\"localhost\",\"input\":\"source_topic\",\"output\":\"destination_topic\",\"process\":\"msg.payload = \\\"* \\\"+msg.payload+\\\" *\\\";\\nreturn msg;\"}","repeat":"","crontab":"","once":false,"x":150,"y":131,"z":"911370d8.e61a48","wires":[["50abf75f.4e47f8"]]},{"id":"50abf75f.4e47f8","type":"function","name":"initialise","func":"// create the parameters object from the incoming JSON object\nconsole.log(msg.payload);\nmsg.parameters = JSON.parse(msg.payload);\n\n// we're going to create an array of objects\nmsg.payload = [];\nmsg.id = 0;\n\nreturn msg;","outputs":1,"x":292,"y":131,"z":"911370d8.e61a48","wires":[["278fa0eb.43aed8"]]},{"id":"15e5103c.e73b7","type":"function","name":"MQTT in node","func":"// pass in msg.parameters.input\n\nnode_type = \"mqtt in\";\nprevious_id = msg.id;\n\nmsg.id = msg.id + 1;\n\nmsg.payload.push({\n        id: msg.id,\n        type: node_type,\n        topic: msg.parameters.input,\n        broker: msg.defs.broker,\n        name: \"input\",\n\t\tx: 100,\n\t\ty: 100,\n\t\twires: []\n      });\n\nreturn msg;","outputs":1,"x":461,"y":235,"z":"911370d8.e61a48","wires":[["5231e2ad.f01a3c"]]},{"id":"5231e2ad.f01a3c","type":"function","name":"function node","func":"// pass in msg.parameters.process\n\nnode_type = \"function\";\nprevious_id = msg.id;\n\nmsg.id = msg.id + 1;\n\n// fill in the wires link in previous node\nmsg.payload[msg.payload.length-1].wires.push([msg.id]);\nnew_x = msg.payload[msg.payload.length-1].x + msg.defs.spacing;\nnew_y = msg.payload[msg.payload.length-1].y;\n\nmsg.payload.push({\n        id: msg.id,\n        type: node_type,\n        name: \"process\",\n        func: msg.parameters.process,\n        outputs: 1,\n\t\tx: new_x,\n\t\ty: new_y,\n\t\twires: []\n      });\n\nreturn msg;","outputs":1,"x":486,"y":279,"z":"911370d8.e61a48","wires":[["8cf45583.109bf8"]]},{"id":"8cf45583.109bf8","type":"function","name":"MQTT out node","func":"// pass in msg.parameters.output\n \t\t   \n\nnode_type = \"mqtt out\";\nprevious_id = msg.id;\n\nmsg.id = msg.id + 1;\n\n// fill in the wires link in previous node\nmsg.payload[msg.payload.length-1].wires.push([msg.id]);\nnew_x = msg.payload[msg.payload.length-1].x + msg.defs.spacing;\nnew_y = msg.payload[msg.payload.length-1].y;\n\n\nmsg.payload.push({\n        id: msg.id,\n        type: node_type,\n        topic: msg.parameters.output,\n        broker: msg.defs.broker,\n        name: \"output\",\n\t\tx: new_x,\n\t\ty: new_y,\n\t\twires: []\n      });\n\nreturn msg;","outputs":1,"x":515,"y":326,"z":"911370d8.e61a48","wires":[["a3f81690.493398"]]},{"id":"a3f81690.493398","type":"debug","name":"","active":true,"complete":"false","x":673,"y":326,"z":"911370d8.e61a48","wires":[]},{"id":"485c51ed.6013b8","type":"comment","name":"generate \"mqtt - process - mqtt\" flow","info":"publish  to \"configure\" topic:\n\n{\n  \"broker\":\"localhost\",\n  \"input\":\"source_topic\",\n  \"output\":\"destination_topic\",\n  \"process\":\"msg.payload = \\\"* \\\"+msg.payload+\\\" *\\\";\\nreturn msg;\"\n}","x":199,"y":73,"z":"911370d8.e61a48","wires":[]}]