Help with rule and string within a string

Setup, Configuration and Use Scripts & Rules
1

Anyone know how i can pull the value of rad out of this string in a rule to update an item. This is a little different then normal as its a string within a string so the traditional method isnt working…

{"_type":"waypoints","waypoints":[{"_type":"waypoint","tst":1486582266,"lat":42.771794842596,"lon":-78.834592094718,"rad":0,"desc":"Home"}]}
2

That is a json string!
If you have that string in the variable JSON_String it should be:

  var Number myRad = transform("JSONPATH",  "$.waypoints[0].rad", JSON_String)

The “.waypoints[0]” is calling the first element in the Waypoint array. Your posted string contains one item!

1 Like
3

Yes im trying to change this rule into that. This rule works for normal waypoint updates but when you manually push update waypoints it sends a string in a string which is different so this rule dont see it…

rule "OwnTracks Waypoint Jay"
  when
    Item JCWayPointData received update
  then
  logInfo("MQTT", "OwnTracks waypoint updated for Jay")
    val String json = (JCWayPointData.state as StringType).toString
    val String type = transform("JSONPATH", "$._type", json)
    if (type == "waypoints") {
      val String desc = transform("JSONPATH", "$.desc", json)
      JCRadius.postUpdate(desc)
      logInfo("OwnTracks", "Jay is at " + desc)
    }
end
4

The json you posted above has a waypoint of type “waypoint”, the code you posted only reads “transition”.

5

Yea i know, forget about that part… im just looking for the correct string to use in that rule to pull the data i need when i manually push update waypoint :wink:

6

i just keep getting “given new state is NULL, couldn’t post update for ‘JCRadius’” cause it cant read the above string properly

7

You changedthe posted code, however now it will reads “waypoints”, that is the name of the array! You need “waypoint”!

8

I cant use “waypoint” currently because i cannot read that string in a string. Currently i can only grab the initial “waypoints” from it to use. That’s why i needed help to read that. Then i can change it to the “waypoint” string in there.

This is the manually pushed string: (trying to read this in a rule)

{"_type":"waypoints","waypoints":[{"_type":"waypoint","tst":1486582266,"lat":42.771794842596,"lon":-78.834592094718,"rad":0,"desc":"Home"}]}

and this is the automatically sent string: (no problem reading this in a rule)

{"_type":"waypoint","tst":1486582266,"lat":42.771794842596,"lon":-78.834592094718,"rad":0,"desc":"Home"}

see the difference?

9

I don’t get your problem
The first one can be read with:

var Number myRad = transform(“JSONPATH”, “$.waypoints[0].rad”, JSON_String)

the second with

var Number myRad = transform(“JSONPATH”, “$.rad”, JSON_String)

I used this one to test:

10

This is what i was looking for but how do i use it in the rule? just remove the similar val thats in there?

var Number myRad = transform("JSONPATH",  "$.waypoints[0].rad", JSON_String)
11

All depends on how the json string is posted to the rule! As stated above, the variable JSON-String expects the json as posted above (first example).
I’d use some lines like

logInfo(“CheckMyRule”, “MyCheckedVariable = {}”, MyCheckedVariable)

Make a test-run and look into the log! (Using karafs log:tail!)

12

Its posted exactly like this:

{"_type":"waypoints","waypoints":[{"_type":"waypoint","tst":1486582266,"lat":42.771794842596,"lon":-78.834592094718,"rad":0,"desc":"Home"}]}

Trying this with no luck…

rule "OwnTracks Waypoint Jay"
  when
    Item JCWayPointData received update
  then
  logInfo("MQTT", "OwnTracks waypoint updated for Jay")
    val String json = (JCWayPointData.state as StringType).toString
    var Number myType = transform("JSONPATH",  "$.waypoints[0]._type", JSON_String)
    if (mytype == "waypoint") {
      val String myRad = transform("JSONPATH",  "$.waypoints[0].rad", JSON_String)
      JCRadius.postUpdate(rad)
      logInfo("OwnTracks", "Jay is at " + desc)
    }
end
13

Error during the execution of rule ‘OwnTracks Waypoint Jay’: The name ‘JSON_String’ cannot be resolved to an item or type.
2017-02-11 11:26:08.331 [WARN ] [.c.i.events.EventPublisherImpl] - given new state is NULL, couldn’t post update for 'JCRadius’
2017-02-11 11:26:08.562 [INFO ] [openhab.model.script.OwnTracks] - Jay is at null

14

Tried this also,

rule "OwnTracks Waypoint Jay"
  when
    Item JCWayPointData received update
  then
  logInfo("MQTT", "OwnTracks waypoint updated for Jay")
    val String json = (JCWayPointData.state as StringType).toString
    var String myType = transform("JSONPATH",  "$.waypoints[0]._type", JSON_String)
    if (myType == "waypoint") {
      val String myRad = transform("JSONPATH",  "$.waypoints[0].rad", JSON_String)
      JCRadius.postUpdate(myRad)
      logInfo("OwnTracks", "Jay is at " + desc)
    }
end
15

You used the name “JSON_String” from my example, however your string is named “json”!!!

1 Like
16

owwwww let me try

17

You are the man! thanks so much!!!

Cheers!

18

Works like a charm for manual waypoint sending.

rule "OwnTracks Waypoint Jay"
  when
    Item JCWayPointData received update
  then
  logInfo("MQTT", "OwnTracks waypoint updated for Jay")
    val String json = (JCWayPointData.state as StringType).toString
    var String myType = transform("JSONPATH",  "$.waypoints[0]._type", json)
    if (myType == "waypoint") {
      val String myDesc = transform("JSONPATH",  "$.waypoints[0].desc", json)
      JCRadius.postUpdate(myDesc)
      logInfo("OwnTracks", "Jay is at " + myDesc)
    }
end