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Added note about template triggers (#4018)

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Added an entity_id to the template trigger, as is best practice. Added a warning that template triggers without an entity_id have major performance impacts, and directing people to template sensors as an alternative.
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DubhAd 2017-11-19 21:04:00 +00:00 committed by Franck Nijhof
parent 2b35375582
commit 2bd161d258
1 changed files with 5 additions and 0 deletions
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source/_docs/automation/trigger.markdown
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@ -138,6 +138,10 @@ The US Naval Observatory has a [tool](http://aa.usno.navy.mil/data/docs/AltAz.ph
### {% linkable_title Template trigger %}
<p class='note warning'>
If your template trigger has no `entity_id` listed, then it is evaluted on *every* state change for *every* entity. Instead you should create a [template sensor](/components/sensor.template/) or [template binary sensor](/components/binary_sensor.template/) and use that in your automation.
</p>
Template triggers work by evaluating a [template] on each state change. The trigger will fire if the state change caused the template to render 'true'. This is achieved by having the template result in a true boolean expression (`{% raw %}{{ is_state('device_tracker.paulus', 'home') }}{% endraw %}`) or by having the template render 'true' (example below).
With template triggers you can also evaluate attribute changes by using is_state_attr (`{% raw %}{{ is_state_attr('climate.living_room', 'away_mode', 'off') }}{% endraw %}`)
@ -145,6 +149,7 @@ With template triggers you can also evaluate attribute changes by using is_state
automation:
trigger:
platform: template
entity_id: device_tracker.paulus
value_template: "{% raw %}{% if is_state('device_tracker.paulus', 'home') %}true{% endif %}{% endraw %}"
```