SVGHMI: JsonTable now use intermediate variables again to address JSON data without duplicating code or referencing. Using intermediate variables also alows to check for availability of data and stop evaluating early if data is missing. Finally added complete roundtrip example to illustrate use of JSonTable to display "alarms" collected in python from changes on PLC boolean variables.

These classes are intended for use server-side.

e.g. in a django view.py :

    from pyjs.jsonrpc.django import JSONService, jsonremote

    jsonservice = JSONRPCService()

    @jsonremote(jsonservice)
    def test(request, echo_param):
         return "echoing the param back: %s" % echo_param