Writing structs through REST API

jannes · December 2019

Hi,

I have a python3 application running where I use REST API to communicate with the RTM. I've got everything working except for writing variables which are a struct variable. Reading variables (including structs) does work, so does writing non-struct variables.

For writing variables i use a POST method:

r = requests.put(url=url, headers=headers, data=json.dumps(payload), verify=False)

While I debug and run, the arguments would end up with these values:

url: 'https://192.168.100.125/_pxc_api/api/variables/'

headers: {'Authorization': 'Bearer 64ef2acc6444b9ee'}

data: '{"variables": [{"path": "Arp.Plc.Eclr/test", "value": {"i1": 0, "i2": 33}}]}'

The request method will answer with this response:

{'Server': 'nginx', 'Date': 'Thu, 19 Dec 2019 14:14:36 GMT', 'Content-Type': 'application/json', 'Content-Length': '198', 'Connection': 'keep-alive', 'Status': '200 OK', 'Cache-Control': 'no-cache'}

b'{"apiVersion":"1.2.0.0","projectCRC":323846263,"userAuthenticationRequired":true,"variables":[{"path":"Arp.Plc.Eclr/test","value":{"i1":0,"i2":0},"uri":"/_pxc_api/api/variables/Arp.Plc.Eclr/test"}]}'

The response says ok, but the values have not updated

The following is the value of the data argument for a non-struct integer variable which does work:

'{"variables": [{"path": "Arp.Plc.Eclr/alive", "value": 33}]}'

Is it possible to update struct variables that way?

Oliver PLCnext Team · December 2019

Hello jannes,
I think you will have to do something like this.
Take the Variable link as a PathPrefix and the Path as the Stuct element.<br /><br />


The thing that comes to my mind is:
->how to handle multi layer nested types efficiently?{
  "sessionID": "%OptionalSessionID%",
  "pathPrefix": "Arp.Plc.Eclr/Instance.Program.testStruct",
  "variables":
  [
    {
    "path": "i1",
    "value": "%ConstantValue1%",
    }, 
    {
    "path": "i2",
    "value": "%ConstantValueN%",
    "valueType": "Constant"
    }
  ]
}<br /><br />I dont find any hints of key:value pairs for struct in the documentation.

I will see if we have this planed as a feature at the moment.

kind regards,
Oliver

Writing structs through REST API

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