Extracting Event data from a "state_changed" event with a template sensor. How?

Configuration
1

In NodeRED, I can use an event node and a switch to filter out specific event types (state_changed) so I can pull the data from the event bus, then store it in context variables.

I’m wondering how I can also do the same thing using yaml.

I have the following template sensor, but I’m struggling with the syntax, I think. I’m getting “unavailable” as the state.

- trigger:
    - platform: event
      event_type: "state_changed"
      event_data:
        entity_id: input_button.fair_play_task_home_garbage
  sensor:
    - name: "Fair Play Task Home Garbage Last"
      state: "{{trigger}}"
      attributes:
        old_state: "{{trigger.event.old_state.state}}"
        new_state: "{{trigger.event.new_state.state}}"

As you can see, I want to watch the input_button only for a change of state. Then, I want to assign various values of that event to the attributes of the sensor.

I must be missing something in how this works.

2

You have forgotten the data in your templates:

        old_state: "{{trigger.event.data.old_state.state}}"

Also, you should probably not use trigger as the state… it’s just going to be a mess.

3

It can be a bit more concise with a State Trigger.

- trigger:
    - platform: state
      target:
        entity_id: input_button.fair_play_task_home_garbage
      to:
  sensor:
    - name: "Fair Play Task Home Garbage Last"
      state: "{{trigger}}"
      attributes:
        old_state: "{{trigger.from_state.state}}"
        new_state: "{{trigger.to_state.state}}"
1 Like
4

With “event” I believe I have access to more data, correct?

5

Like what exactly?

Here are the State object’s properties.

6

Did the concise example I posted above answer your question or is there something more you require?

7

I chose this path, and it works:

- trigger:
    - platform: event
      event_type: "state_changed"
      event_data:
        entity_id: input_button.fair_play_task_home_garbage
  sensor:
    - name: "Fair Play Task Home Garbage"
      state: "Hello"
      attributes:
        old_state: "{{as_local(as_datetime(trigger.event.data.old_state.state))}}"
        new_state: "{{as_local(as_datetime(trigger.event.data.new_state.state))}}"
        timer: "Handled by NodeRED"

As you can see, the state of the sensor really doesn’t matter. I just wanted to create a sensor that I can use to create a new sensor that will serve as a measure of how much time passes between each state change, which will be written to a spreadsheet.

8

It’s my understanding there’s a performance penalty for employing an Event Trigger, compared to a State Trigger, with no added benefit for this application (which happens to be an ideal candidate for a State Trigger).

Anyway, you asked for advice and you’re free to ignore it. Glad to hear it works for you.

9

That makes perfect sense event if it is filtered. I’ll switch it up to the state since the result would be the same.